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Subject: Re: [PATCH 7/7] media: stm32-dma2d: STM32 DMA2D driver
To:     dillon.minfei@gmail.com, mchehab@kernel.org,
        mchehab+huawei@kernel.org, ezequiel@collabora.com,
        gnurou@gmail.com, pihsun@chromium.org, mcoquelin.stm32@gmail.com,
        alexandre.torgue@foss.st.com, mturquette@baylibre.com,
        sboyd@kernel.org, robh+dt@kernel.org
Cc:     patrice.chotard@foss.st.com, hugues.fruchet@foss.st.com,
        linux-media@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-stm32@st-md-mailman.stormreply.com,
        linux-arm-kernel@lists.infradead.org, linux-clk@vger.kernel.org,
        devicetree@vger.kernel.org
References: <1621508727-24486-1-git-send-email-dillon.minfei@gmail.com>
 <1621508727-24486-8-git-send-email-dillon.minfei@gmail.com>
From:   Hans Verkuil <hverkuil-cisco@xs4all.nl>
Message-ID: <d1a4f9a2-a059-5e3c-867e-85eaf241f9b5@xs4all.nl>
Date:   Thu, 17 Jun 2021 12:18:40 +0200
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Hi Dillon,

Please run checkpatch.pl --strict over this patch: I get too many 'CHECK' warnings.

On 20/05/2021 13:05, dillon.minfei@gmail.com wrote:
> From: Dillon Min <dillon.minfei@gmail.com>
> 
> This V4L2 subdev m2m driver enables Chrom-Art Accelerator unit
> of STMicroelectronics STM32 SoC series.
> 
> Currently support r2m, m2m, m2m_pfc.

What does this mean?

> 
> Signed-off-by: Dillon Min <dillon.minfei@gmail.com>
> ---
>  drivers/media/platform/Kconfig                  |   9 +
>  drivers/media/platform/Makefile                 |   1 +
>  drivers/media/platform/stm32/Makefile           |   2 +
>  drivers/media/platform/stm32/dma2d/dma2d-hw.c   | 143 +++++
>  drivers/media/platform/stm32/dma2d/dma2d-regs.h | 114 ++++
>  drivers/media/platform/stm32/dma2d/dma2d.c      | 791 ++++++++++++++++++++++++
>  drivers/media/platform/stm32/dma2d/dma2d.h      | 132 ++++
>  7 files changed, 1192 insertions(+)
>  create mode 100644 drivers/media/platform/stm32/dma2d/dma2d-hw.c
>  create mode 100644 drivers/media/platform/stm32/dma2d/dma2d-regs.h
>  create mode 100644 drivers/media/platform/stm32/dma2d/dma2d.c
>  create mode 100644 drivers/media/platform/stm32/dma2d/dma2d.h
> 
> diff --git a/drivers/media/platform/Kconfig b/drivers/media/platform/Kconfig
> index 157c924686e4..128f4420623f 100644
> --- a/drivers/media/platform/Kconfig
> +++ b/drivers/media/platform/Kconfig
> @@ -244,6 +244,15 @@ config VIDEO_CODA
>  config VIDEO_IMX_VDOA
>  	def_tristate VIDEO_CODA if SOC_IMX6Q || COMPILE_TEST
>  
> +config VIDEO_STM32_DMA2D
> +	tristate "STM32 Chrom-Art Accelerator (DMA2D)"
> +	depends on VIDEO_DEV && VIDEO_V4L2 && ARCH_STM32

This needs to depend on COMPILE_TEST as well.

> +	select VIDEOBUF2_DMA_CONTIG
> +	select V4L2_MEM2MEM_DEV
> +	help
> +	  The STM32 DMA2D is a memory-to-memory engine for pixel conversion,
> +	  specialized DMA dedicated to image manipulation

Missing period at the end. And the , should probably be replaced with 'and'.

> +
>  config VIDEO_IMX_PXP
>  	tristate "i.MX Pixel Pipeline (PXP)"
>  	depends on VIDEO_DEV && VIDEO_V4L2 && (ARCH_MXC || COMPILE_TEST)
> diff --git a/drivers/media/platform/Makefile b/drivers/media/platform/Makefile
> index eedc14aafb32..93b2b319a2b2 100644
> --- a/drivers/media/platform/Makefile
> +++ b/drivers/media/platform/Makefile
> @@ -69,6 +69,7 @@ obj-$(CONFIG_VIDEO_ATMEL_ISC)		+= atmel/
>  obj-$(CONFIG_VIDEO_ATMEL_ISI)		+= atmel/
>  
>  obj-$(CONFIG_VIDEO_STM32_DCMI)		+= stm32/
> +obj-$(CONFIG_VIDEO_STM32_DMA2D)		+= stm32/
>  
>  obj-$(CONFIG_VIDEO_MEDIATEK_VPU)	+= mtk-vpu/
>  
> diff --git a/drivers/media/platform/stm32/Makefile b/drivers/media/platform/stm32/Makefile
> index 48b36db2c2e2..896ef98a73ab 100644
> --- a/drivers/media/platform/stm32/Makefile
> +++ b/drivers/media/platform/stm32/Makefile
> @@ -1,2 +1,4 @@
>  # SPDX-License-Identifier: GPL-2.0-only
>  obj-$(CONFIG_VIDEO_STM32_DCMI) += stm32-dcmi.o
> +stm32-dma2d-objs := dma2d/dma2d.o dma2d/dma2d-hw.o
> +obj-$(CONFIG_VIDEO_STM32_DMA2D) += stm32-dma2d.o
> diff --git a/drivers/media/platform/stm32/dma2d/dma2d-hw.c b/drivers/media/platform/stm32/dma2d/dma2d-hw.c
> new file mode 100644
> index 000000000000..6fdbf5a21151
> --- /dev/null
> +++ b/drivers/media/platform/stm32/dma2d/dma2d-hw.c
> @@ -0,0 +1,143 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * ST stm32 Chrom-Art - 2D Graphics Accelerator Driver
> + *
> + * Copyright (c) 2021 Dillon Min
> + * Dillon Min, <dillon.minfei@gmail.com>
> + *
> + * based on s5p-g2d
> + *
> + * Copyright (c) 2011 Samsung Electronics Co., Ltd.
> + * Kamil Debski, <k.debski@samsung.com>
> + */
> +
> +#include <linux/io.h>
> +
> +#include "dma2d.h"
> +#include "dma2d-regs.h"
> +
> +static inline u32 reg_read(void __iomem *base, u32 reg)
> +{
> +	return readl_relaxed(base + reg);
> +}
> +
> +static inline void reg_write(void __iomem *base, u32 reg, u32 val)
> +{
> +	writel_relaxed(val, base + reg);
> +}
> +
> +static inline void reg_set(void __iomem *base, u32 reg, u32 mask)
> +{
> +	reg_write(base, reg, reg_read(base, reg) | mask);
> +}
> +
> +static inline void reg_clear(void __iomem *base, u32 reg, u32 mask)
> +{
> +	reg_write(base, reg, reg_read(base, reg) & ~mask);
> +}
> +
> +static inline void reg_update_bits(void __iomem *base, u32 reg, u32 mask,
> +		u32 val)
> +{
> +	reg_write(base, reg, (reg_read(base, reg) & ~mask) | val);
> +}
> +
> +void dma2d_start(struct dma2d_dev *d)
> +{
> +	reg_update_bits(d->regs, DMA2D_CR_REG, CR_START, CR_START);
> +}
> +
> +u32 dma2d_get_int(struct dma2d_dev *d)
> +{
> +	return reg_read(d->regs, DMA2D_ISR_REG);
> +}
> +
> +void dma2d_clear_int(struct dma2d_dev *d)
> +{
> +	u32 isr_val = reg_read(d->regs, DMA2D_ISR_REG);
> +
> +	reg_write(d->regs, DMA2D_IFCR_REG, isr_val & 0x003f);
> +}
> +
> +void dma2d_config_common(struct dma2d_dev *d, enum dma2d_op_mode op_mode,
> +		u16 width, u16 height)
> +{
> +	reg_update_bits(d->regs, DMA2D_CR_REG, CR_MODE_MASK,
> +		op_mode << CR_MODE_SHIFT);
> +
> +	reg_write(d->regs, DMA2D_NLR_REG, (width << 16) | height);
> +}
> +
> +void dma2d_config_out(struct dma2d_dev *d, struct dma2d_frame *frm,
> +		dma_addr_t o_addr)
> +{
> +	reg_update_bits(d->regs, DMA2D_CR_REG, CR_CEIE, CR_CEIE);
> +	reg_update_bits(d->regs, DMA2D_CR_REG, CR_CTCIE, CR_CTCIE);
> +	reg_update_bits(d->regs, DMA2D_CR_REG, CR_CAEIE, CR_CAEIE);
> +	reg_update_bits(d->regs, DMA2D_CR_REG, CR_TCIE, CR_TCIE);
> +	reg_update_bits(d->regs, DMA2D_CR_REG, CR_TEIE, CR_TEIE);
> +
> +	if (frm->fmt->cmode >= CM_MODE_ARGB8888 &&
> +		frm->fmt->cmode <= CM_MODE_ARGB4444)
> +		reg_update_bits(d->regs, DMA2D_OPFCCR_REG, OPFCCR_CM_MASK,
> +			frm->fmt->cmode);
> +
> +	reg_write(d->regs, DMA2D_OMAR_REG, o_addr);
> +
> +	reg_write(d->regs, DMA2D_OCOLR_REG,
> +		(frm->a_rgb[3] << 24) |
> +		(frm->a_rgb[2] << 16) |
> +		(frm->a_rgb[1] << 8) |
> +		frm->a_rgb[0]);
> +
> +	reg_update_bits(d->regs, DMA2D_OOR_REG, OOR_LO_MASK,
> +			frm->line_ofs & 0x3fff);
> +}
> +
> +void dma2d_config_fg(struct dma2d_dev *d, struct dma2d_frame *frm,
> +		dma_addr_t f_addr)
> +{
> +	reg_write(d->regs, DMA2D_FGMAR_REG, f_addr);
> +	reg_update_bits(d->regs, DMA2D_FGOR_REG, FGOR_LO_MASK,
> +			frm->line_ofs);
> +
> +	if (frm->fmt->cmode >= CM_MODE_ARGB8888 &&
> +		frm->fmt->cmode <= CM_MODE_A4)
> +		reg_update_bits(d->regs, DMA2D_FGPFCCR_REG, FGPFCCR_CM_MASK,
> +			frm->fmt->cmode);
> +
> +	reg_update_bits(d->regs, DMA2D_FGPFCCR_REG, FGPFCCR_AM_MASK,
> +			(frm->a_mode << 16) & 0x03);
> +
> +	reg_update_bits(d->regs, DMA2D_FGPFCCR_REG, FGPFCCR_ALPHA_MASK,
> +			frm->a_rgb[3] << 24);
> +
> +	reg_write(d->regs, DMA2D_FGCOLR_REG,
> +		(frm->a_rgb[2] << 16) |
> +		(frm->a_rgb[1] << 8) |
> +		frm->a_rgb[0]);
> +}
> +
> +void dma2d_config_bg(struct dma2d_dev *d, struct dma2d_frame *frm,
> +		dma_addr_t b_addr)
> +{
> +	reg_write(d->regs, DMA2D_BGMAR_REG, b_addr);
> +	reg_update_bits(d->regs, DMA2D_BGOR_REG, BGOR_LO_MASK,
> +			frm->line_ofs);
> +
> +	if (frm->fmt->cmode >= CM_MODE_ARGB8888 &&
> +		frm->fmt->cmode <= CM_MODE_A4)
> +		reg_update_bits(d->regs, DMA2D_BGPFCCR_REG, BGPFCCR_CM_MASK,
> +			frm->fmt->cmode);
> +
> +	reg_update_bits(d->regs, DMA2D_BGPFCCR_REG, BGPFCCR_AM_MASK,
> +			(frm->a_mode << 16) & 0x03);
> +
> +	reg_update_bits(d->regs, DMA2D_BGPFCCR_REG, BGPFCCR_ALPHA_MASK,
> +			frm->a_rgb[3] << 24);
> +
> +	reg_write(d->regs, DMA2D_BGCOLR_REG,
> +		(frm->a_rgb[2] << 16) |
> +		(frm->a_rgb[1] << 8) |
> +		frm->a_rgb[0]);
> +}
> diff --git a/drivers/media/platform/stm32/dma2d/dma2d-regs.h b/drivers/media/platform/stm32/dma2d/dma2d-regs.h
> new file mode 100644
> index 000000000000..6e375bcb1281
> --- /dev/null
> +++ b/drivers/media/platform/stm32/dma2d/dma2d-regs.h
> @@ -0,0 +1,114 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +/*
> + * ST stm32 Chrom-Art - 2D Graphics Accelerator Driver
> + *
> + * Copyright (c) 2021 Dillon Min
> + * Dillon Min, <dillon.minfei@gmail.com>
> + *
> + * based on s5p-g2d
> + *
> + * Copyright (c) 2011 Samsung Electronics Co., Ltd.
> + * Kamil Debski, <k.debski@samsung.com>
> + */
> +
> +#ifndef __DMA2D_REGS_H__
> +#define __DMA2D_REGS_H__
> +
> +#define DMA2D_CR_REG		0x0000
> +#define CR_MODE_MASK		GENMASK(17, 16)
> +#define CR_MODE_SHIFT		16
> +#define CR_M2M			0x0000
> +#define CR_M2M_PFC		BIT(16)
> +#define CR_M2M_BLEND		BIT(17)
> +#define CR_R2M			(BIT(17) | BIT(16))
> +#define CR_CEIE			BIT(13)
> +#define CR_CTCIE		BIT(12)
> +#define CR_CAEIE		BIT(11)
> +#define CR_TWIE			BIT(10)
> +#define CR_TCIE			BIT(9)
> +#define CR_TEIE			BIT(8)
> +#define CR_ABORT		BIT(2)
> +#define CR_SUSP			BIT(1)
> +#define CR_START		BIT(0)
> +
> +#define DMA2D_ISR_REG		0x0004
> +#define ISR_CEIF		BIT(5)
> +#define ISR_CTCIF		BIT(4)
> +#define ISR_CAEIF		BIT(3)
> +#define ISR_TWIF		BIT(2)
> +#define ISR_TCIF		BIT(1)
> +#define ISR_TEIF		BIT(0)
> +
> +#define DMA2D_IFCR_REG		0x0008
> +#define IFCR_CCEIF		BIT(5)
> +#define IFCR_CCTCIF		BIT(4)
> +#define IFCR_CAECIF		BIT(3)
> +#define IFCR_CTWIF		BIT(2)
> +#define IFCR_CTCIF		BIT(1)
> +#define IFCR_CTEIF		BIT(0)
> +
> +#define DMA2D_FGMAR_REG		0x000c
> +#define DMA2D_FGOR_REG		0x0010
> +#define FGOR_LO_MASK		GENMASK(13, 0)
> +
> +#define DMA2D_BGMAR_REG		0x0014
> +#define DMA2D_BGOR_REG		0x0018
> +#define BGOR_LO_MASK		GENMASK(13, 0)
> +
> +#define DMA2D_FGPFCCR_REG	0x001c
> +#define FGPFCCR_ALPHA_MASK	GENMASK(31, 24)
> +#define FGPFCCR_AM_MASK		GENMASK(17, 16)
> +#define FGPFCCR_CS_MASK		GENMASK(15, 8)
> +#define FGPFCCR_START		BIT(5)
> +#define FGPFCCR_CCM_RGB888	BIT(4)
> +#define FGPFCCR_CM_MASK		GENMASK(3, 0)
> +
> +#define DMA2D_FGCOLR_REG	0x0020
> +#define FGCOLR_REG_MASK		GENMASK(23, 16)
> +#define FGCOLR_GREEN_MASK	GENMASK(15, 8)
> +#define FGCOLR_BLUE_MASK	GENMASK(7, 0)
> +
> +#define DMA2D_BGPFCCR_REG	0x0024
> +#define BGPFCCR_ALPHA_MASK	GENMASK(31, 24)
> +#define BGPFCCR_AM_MASK		GENMASK(17, 16)
> +#define BGPFCCR_CS_MASK		GENMASK(15, 8)
> +#define BGPFCCR_START		BIT(5)
> +#define BGPFCCR_CCM_RGB888	BIT(4)
> +#define BGPFCCR_CM_MASK		GENMASK(3, 0)
> +
> +#define DMA2D_BGCOLR_REG	0x0028
> +#define BGCOLR_REG_MASK		GENMASK(23, 16)
> +#define BGCOLR_GREEN_MASK	GENMASK(15, 8)
> +#define BGCOLR_BLUE_MASK	GENMASK(7, 0)
> +
> +#define DMA2D_OPFCCR_REG	0x0034
> +#define OPFCCR_CM_MASK		GENMASK(2, 0)
> +
> +#define DMA2D_OCOLR_REG		0x0038
> +#define OCOLR_ALPHA_MASK	GENMASK(31, 24)
> +#define OCOLR_RED_MASK		GENMASK(23, 16)
> +#define OCOLR_GREEN_MASK	GENMASK(15, 8)
> +#define OCOLR_BLUE_MASK		GENMASK(7, 0)
> +
> +#define DMA2D_OMAR_REG		0x003c
> +
> +#define DMA2D_OOR_REG		0x0040
> +#define OOR_LO_MASK		GENMASK(13, 0)
> +
> +#define DMA2D_NLR_REG		0x0044
> +#define NLR_PL_MASK		GENMASK(29, 16)
> +#define NLR_NL_MASK		GENMASK(15, 0)
> +
> +
> +/* Hardware limits */
> +#define MAX_WIDTH		0x3fff
> +#define MAX_HEIGHT		0xffff
> +
> +#define DEFAULT_WIDTH		240
> +#define DEFAULT_HEIGHT		320
> +#define DEFAULT_SIZE		307200
> +
> +#define CM_MODE_ARGB8888	0x00
> +#define CM_MODE_ARGB4444	0x04
> +#define CM_MODE_A4		0x0a
> +#endif /* __DMA2D_REGS_H__ */
> diff --git a/drivers/media/platform/stm32/dma2d/dma2d.c b/drivers/media/platform/stm32/dma2d/dma2d.c
> new file mode 100644
> index 000000000000..88f8333a174a
> --- /dev/null
> +++ b/drivers/media/platform/stm32/dma2d/dma2d.c
> @@ -0,0 +1,791 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * STM32 DMA2D - 2D Graphics Accelerator Driver
> + *
> + * Copyright (c) 2021 Dillon Min
> + * Dillon Min, <dillon.minfei@gmail.com>
> + *
> + * based on s5p-g2d
> + *
> + * Copyright (c) 2011 Samsung Electronics Co., Ltd.
> + * Kamil Debski, <k.debski@samsung.com>
> + */
> +
> +#include <linux/module.h>
> +#include <linux/fs.h>
> +#include <linux/timer.h>
> +#include <linux/sched.h>
> +#include <linux/slab.h>
> +#include <linux/clk.h>
> +#include <linux/interrupt.h>
> +#include <linux/of.h>
> +
> +#include <linux/platform_device.h>
> +#include <media/v4l2-mem2mem.h>
> +#include <media/v4l2-device.h>
> +#include <media/v4l2-ioctl.h>
> +#include <media/v4l2-event.h>
> +#include <media/videobuf2-v4l2.h>
> +#include <media/videobuf2-dma-contig.h>
> +
> +#include "dma2d.h"
> +#include "dma2d-regs.h"
> +
> +#define fh2ctx(__fh) container_of(__fh, struct dma2d_ctx, fh)
> +
> +static struct dma2d_fmt formats[] = {

Can this be const?

> +	{
> +		.fourcc	= V4L2_PIX_FMT_ARGB32,
> +		.cmode = DMA2D_CMODE_ARGB8888,
> +		.depth = 32,
> +	},
> +	{
> +		.fourcc	= V4L2_PIX_FMT_RGB24,
> +		.cmode = DMA2D_CMODE_RGB888,
> +		.depth = 24,
> +	},
> +	{
> +		.fourcc	= V4L2_PIX_FMT_RGB565,
> +		.cmode = DMA2D_CMODE_RGB565,
> +		.depth = 16,
> +	},
> +	{
> +		.fourcc	= V4L2_PIX_FMT_ARGB555,
> +		.cmode = DMA2D_CMODE_ARGB1555,
> +		.depth = 16,
> +	},
> +	{
> +		.fourcc	= V4L2_PIX_FMT_ARGB444,
> +		.cmode = DMA2D_CMODE_ARGB4444,
> +		.depth = 16,
> +	},
> +};
> +#define NUM_FORMATS ARRAY_SIZE(formats)
> +
> +static struct dma2d_frame def_frame = {

Ditto.

> +	.width		= DEFAULT_WIDTH,
> +	.height		= DEFAULT_HEIGHT,
> +	.line_ofs	= 0,

Does 'ofs' stand for 'offset'? If so, then I prefer the full 'offset' over 'ofs'.
'ofs' is a bit obscure.

> +	.a_rgb		= {0x00, 0x00, 0x00, 0xff},
> +	.a_mode		= DMA2D_ALPHA_MODE_NO_MODIF,
> +	.fmt		= &formats[0],
> +	.size		= DEFAULT_SIZE,
> +};
> +
> +static struct dma2d_fmt *find_fmt(int pixelformat)
> +{
> +	unsigned int i;
> +
> +	for (i = 0; i < NUM_FORMATS; i++) {
> +		if (formats[i].fourcc == pixelformat)
> +			return &formats[i];
> +	}
> +
> +	return NULL;
> +}
> +
> +static struct dma2d_frame *get_frame(struct dma2d_ctx *ctx,
> +				   enum v4l2_buf_type type)
> +{
> +	switch (type) {
> +	case V4L2_BUF_TYPE_VIDEO_OUTPUT:
> +		return &ctx->fg;
> +	case V4L2_BUF_TYPE_VIDEO_CAPTURE:
> +		return &ctx->out;

Hmm, capture returns ctx->out, and output returns ctx->fg. Not exactly what
you would expect.

> +	default:
> +		return ERR_PTR(-EINVAL);

Using error pointers here is a bit overkill IMHO. I think returning NULL is
typical. With a WARN_ON perhaps since this really shouldn't happen.

Alternatively just do this:

	return V4L2_TYPE_IS_OUTPUT(type) ? &ctx->fg : &ctx->out;

It avoids the whole problem.

> +	}
> +}
> +
> +static int dma2d_queue_setup(struct vb2_queue *vq,
> +			   unsigned int *nbuffers, unsigned int *nplanes,
> +			   unsigned int sizes[], struct device *alloc_devs[])
> +{
> +	struct dma2d_ctx *ctx = vb2_get_drv_priv(vq);
> +	struct dma2d_frame *f = get_frame(ctx, vq->type);
> +
> +	if (IS_ERR(f))
> +		return PTR_ERR(f);
> +
> +	if (*nplanes)
> +		return sizes[0] < f->size ? -EINVAL : 0;
> +
> +	sizes[0] = f->size;
> +	*nplanes = 1;
> +
> +	if (*nbuffers == 0)
> +		*nbuffers = 1;
> +
> +	return 0;
> +}
> +
> +static int dma2d_buf_out_validate(struct vb2_buffer *vb)
> +{
> +	struct vb2_v4l2_buffer *vbuf = to_vb2_v4l2_buffer(vb);
> +
> +	if (vbuf->field == V4L2_FIELD_ANY)
> +		vbuf->field = V4L2_FIELD_NONE;
> +	if (vbuf->field != V4L2_FIELD_NONE)
> +		return -EINVAL;
> +
> +	return 0;
> +}
> +
> +static int dma2d_buf_prepare(struct vb2_buffer *vb)
> +{
> +	struct dma2d_ctx *ctx = vb2_get_drv_priv(vb->vb2_queue);
> +	struct dma2d_frame *f = get_frame(ctx, vb->vb2_queue->type);
> +
> +	if (IS_ERR(f))
> +		return PTR_ERR(f);
> +
> +	if (vb2_plane_size(vb, 0) < f->size)
> +		return -EINVAL;
> +
> +	vb2_set_plane_payload(vb, 0, f->size);
> +
> +	return 0;
> +}
> +
> +static void dma2d_buf_queue(struct vb2_buffer *vb)
> +{
> +	struct vb2_v4l2_buffer *vbuf = to_vb2_v4l2_buffer(vb);
> +	struct dma2d_ctx *ctx = vb2_get_drv_priv(vb->vb2_queue);
> +
> +	v4l2_m2m_buf_queue(ctx->fh.m2m_ctx, vbuf);
> +}
> +
> +static int dma2d_start_streaming(struct vb2_queue *q, unsigned int count)
> +{
> +	struct dma2d_ctx *ctx = vb2_get_drv_priv(q);
> +	struct dma2d_frame *f = get_frame(ctx, q->type);
> +
> +	if (IS_ERR(f))
> +		return -EINVAL;
> +
> +	f->sequence = 0;
> +	return 0;
> +}
> +
> +static void dma2d_stop_streaming(struct vb2_queue *q)
> +{
> +	struct dma2d_ctx *ctx = vb2_get_drv_priv(q);
> +	struct vb2_v4l2_buffer *vbuf;
> +
> +	for (;;) {
> +		if (V4L2_TYPE_IS_OUTPUT(q->type))
> +			vbuf = v4l2_m2m_src_buf_remove(ctx->fh.m2m_ctx);
> +		else
> +			vbuf = v4l2_m2m_dst_buf_remove(ctx->fh.m2m_ctx);
> +		if (!vbuf)
> +			return;
> +		v4l2_m2m_buf_done(vbuf, VB2_BUF_STATE_ERROR);
> +	}
> +}
> +
> +static const struct vb2_ops dma2d_qops = {
> +	.queue_setup	= dma2d_queue_setup,
> +	.buf_out_validate	 = dma2d_buf_out_validate,
> +	.buf_prepare	= dma2d_buf_prepare,
> +	.buf_queue	= dma2d_buf_queue,
> +	.start_streaming = dma2d_start_streaming,
> +	.stop_streaming  = dma2d_stop_streaming,
> +	.wait_prepare	= vb2_ops_wait_prepare,
> +	.wait_finish	= vb2_ops_wait_finish,
> +};
> +
> +static int queue_init(void *priv, struct vb2_queue *src_vq,
> +						struct vb2_queue *dst_vq)
> +{
> +	struct dma2d_ctx *ctx = priv;
> +	int ret;
> +
> +	src_vq->type = V4L2_BUF_TYPE_VIDEO_OUTPUT;
> +	src_vq->io_modes = VB2_MMAP | VB2_DMABUF;
> +	src_vq->drv_priv = ctx;
> +	src_vq->ops = &dma2d_qops;
> +	src_vq->mem_ops = &vb2_dma_contig_memops;
> +	src_vq->buf_struct_size = sizeof(struct v4l2_m2m_buffer);
> +	src_vq->timestamp_flags = V4L2_BUF_FLAG_TIMESTAMP_COPY;
> +	src_vq->lock = &ctx->dev->mutex;
> +	src_vq->dev = ctx->dev->v4l2_dev.dev;
> +
> +	ret = vb2_queue_init(src_vq);
> +	if (ret)
> +		return ret;
> +
> +	dst_vq->type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
> +	dst_vq->io_modes = VB2_MMAP | VB2_DMABUF;
> +	dst_vq->drv_priv = ctx;
> +	dst_vq->ops = &dma2d_qops;
> +	dst_vq->mem_ops = &vb2_dma_contig_memops;
> +	dst_vq->buf_struct_size = sizeof(struct v4l2_m2m_buffer);
> +	dst_vq->timestamp_flags = V4L2_BUF_FLAG_TIMESTAMP_COPY;
> +	dst_vq->lock = &ctx->dev->mutex;
> +	dst_vq->dev = ctx->dev->v4l2_dev.dev;
> +
> +	return vb2_queue_init(dst_vq);
> +}
> +
> +#define V4L2_CID_DMA2D_R2M_COLOR (V4L2_CID_USER_BASE | 0x1200)
> +#define V4L2_CID_DMA2D_R2M_MODE (V4L2_CID_USER_BASE | 0x1201)

You need to reserve a range for driver-specific controls in include/uapi/linux/v4l2-controls.h.
Search for V4L2_CID_USER_CCS_BASE to see how it is done.

> +static int dma2d_s_ctrl(struct v4l2_ctrl *ctrl)
> +{
> +	struct dma2d_frame *frm;
> +	struct dma2d_ctx *ctx = container_of(ctrl->handler, struct dma2d_ctx,
> +								ctrl_handler);
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&ctx->dev->ctrl_lock, flags);
> +	switch (ctrl->id) {
> +	case V4L2_CID_ALPHA_COMPONENT:
> +		/* set the background alpha value*/
> +		ctx->alpha_component = (u8) ctrl->val;
> +		break;
> +	case V4L2_CID_DMA2D_R2M_COLOR:
> +		frm = get_frame(ctx, V4L2_BUF_TYPE_VIDEO_CAPTURE);
> +		frm->a_rgb[3] = (ctrl->val >> 24) & 0xff;
> +		frm->a_rgb[2] = (ctrl->val >> 16) & 0xff;
> +		frm->a_rgb[1] = (ctrl->val >>  8) & 0xff;
> +		frm->a_rgb[0] = ctrl->val & 0xff;
> +		break;
> +	case V4L2_CID_DMA2D_R2M_MODE:
> +		if (ctrl->val)
> +			ctx->op_mode = DMA2D_MODE_R2M;
> +		break;
> +	default:
> +		v4l2_err(&ctx->dev->v4l2_dev, "Invalid control\n");
> +		spin_unlock_irqrestore(&ctx->dev->ctrl_lock, flags);
> +		return -EINVAL;
> +
> +	}
> +	spin_unlock_irqrestore(&ctx->dev->ctrl_lock, flags);
> +
> +	return 0;
> +}
> +
> +static const struct v4l2_ctrl_ops dma2d_ctrl_ops = {
> +	.s_ctrl	= dma2d_s_ctrl,
> +};
> +
> +static const struct v4l2_ctrl_config dma2d_r2m_control[] = {
> +	{
> +	.ops = &dma2d_ctrl_ops,
> +	.id = V4L2_CID_DMA2D_R2M_COLOR,
> +	.name = "R2M Alpha/Color Value",
> +	.type = V4L2_CTRL_TYPE_INTEGER,
> +	.min = 0xffffffff80000000ULL,
> +	.max = 0x7fffffff,
> +	.def = 0,
> +	.step = 1,
> +	},
> +	{
> +	.ops = &dma2d_ctrl_ops,
> +	.id = V4L2_CID_DMA2D_R2M_MODE,
> +	.name = "Set to r2m mode",

"Set R2M Mode"

These controls need to be documented.

> +	.type = V4L2_CTRL_TYPE_BOOLEAN,
> +	.min = 0,
> +	.max = 1,
> +	.def = 0,
> +	.step = 1,
> +	}
> +};
> +
> +static int dma2d_setup_ctrls(struct dma2d_ctx *ctx)
> +{
> +	v4l2_ctrl_handler_init(&ctx->ctrl_handler, 3);
> +
> +	v4l2_ctrl_new_std(&ctx->ctrl_handler, &dma2d_ctrl_ops,
> +			V4L2_CID_ALPHA_COMPONENT, 0, 255, 1, 255);
> +	v4l2_ctrl_new_custom(&ctx->ctrl_handler, &dma2d_r2m_control[0], NULL);
> +	v4l2_ctrl_new_custom(&ctx->ctrl_handler, &dma2d_r2m_control[1], NULL);
> +
> +	return 0;
> +}
> +
> +static int dma2d_open(struct file *file)
> +{
> +	struct dma2d_dev *dev = video_drvdata(file);
> +	struct dma2d_ctx *ctx = NULL;
> +	int ret = 0;
> +
> +	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
> +	if (!ctx)
> +		return -ENOMEM;
> +	ctx->dev = dev;
> +	/* Set default formats */
> +	ctx->fg		= def_frame;
> +	ctx->bg		= def_frame;
> +	ctx->out	= def_frame;
> +	ctx->op_mode	= DMA2D_MODE_M2M_FPC;
> +	ctx->colorspace = V4L2_COLORSPACE_REC709;
> +	ctx->alpha_component = 0x00;
> +	if (mutex_lock_interruptible(&dev->mutex)) {
> +		kfree(ctx);
> +		return -ERESTARTSYS;
> +	}
> +
> +	ctx->fh.m2m_ctx = v4l2_m2m_ctx_init(dev->m2m_dev, ctx, &queue_init);
> +	if (IS_ERR(ctx->fh.m2m_ctx)) {
> +		ret = PTR_ERR(ctx->fh.m2m_ctx);
> +		mutex_unlock(&dev->mutex);
> +		kfree(ctx);
> +		return ret;
> +	}
> +
> +	v4l2_fh_init(&ctx->fh, video_devdata(file));
> +	file->private_data = &ctx->fh;
> +	v4l2_fh_add(&ctx->fh);
> +
> +	dma2d_setup_ctrls(ctx);
> +
> +	/* Write the default values to the ctx struct */
> +	v4l2_ctrl_handler_setup(&ctx->ctrl_handler);
> +
> +	ctx->fh.ctrl_handler = &ctx->ctrl_handler;
> +	mutex_unlock(&dev->mutex);
> +
> +	return 0;
> +}
> +
> +static int dma2d_release(struct file *file)
> +{
> +	struct dma2d_dev *dev = video_drvdata(file);
> +	struct dma2d_ctx *ctx = fh2ctx(file->private_data);
> +
> +	v4l2_ctrl_handler_free(&ctx->ctrl_handler);
> +	v4l2_fh_del(&ctx->fh);
> +	v4l2_fh_exit(&ctx->fh);
> +	mutex_lock(&dev->mutex);
> +	v4l2_m2m_ctx_release(ctx->fh.m2m_ctx);
> +	mutex_unlock(&dev->mutex);
> +	kfree(ctx);
> +
> +	return 0;
> +}
> +
> +static int vidioc_querycap(struct file *file, void *priv,
> +				struct v4l2_capability *cap)
> +{
> +	strscpy(cap->driver, DMA2D_NAME, sizeof(cap->driver));
> +	strscpy(cap->card, DMA2D_NAME, sizeof(cap->card));
> +	strscpy(cap->bus_info, BUS_INFO, sizeof(cap->bus_info));
> +
> +	return 0;
> +}
> +
> +static int vidioc_enum_fmt(struct file *file, void *prv, struct v4l2_fmtdesc *f)
> +{
> +	if (f->index >= NUM_FORMATS)
> +		return -EINVAL;
> +
> +	f->pixelformat = formats[f->index].fourcc;
> +	return 0;
> +}
> +
> +static int vidioc_g_fmt(struct file *file, void *prv, struct v4l2_format *f)
> +{
> +	struct dma2d_ctx *ctx = prv;
> +	struct vb2_queue *vq;
> +	struct dma2d_frame *frm;
> +
> +	vq = v4l2_m2m_get_vq(ctx->fh.m2m_ctx, f->type);
> +	if (!vq)
> +		return -EINVAL;
> +
> +	frm = get_frame(ctx, f->type);
> +	if (IS_ERR(frm))
> +		return PTR_ERR(frm);
> +
> +	f->fmt.pix.width		= frm->width;
> +	f->fmt.pix.height		= frm->height;
> +	f->fmt.pix.field		= V4L2_FIELD_NONE;
> +	f->fmt.pix.pixelformat		= frm->fmt->fourcc;
> +	f->fmt.pix.bytesperline		= (frm->width * frm->fmt->depth) >> 3;
> +	f->fmt.pix.sizeimage		= frm->size;
> +	f->fmt.pix.colorspace		= ctx->colorspace;
> +	f->fmt.pix.xfer_func		= ctx->xfer_func;
> +	f->fmt.pix.ycbcr_enc		= ctx->ycbcr_enc;
> +	f->fmt.pix.quantization		= ctx->quant;
> +
> +	return 0;
> +}
> +
> +static int vidioc_try_fmt(struct file *file, void *prv, struct v4l2_format *f)
> +{
> +	struct dma2d_ctx *ctx = prv;
> +	struct dma2d_dev *dev = ctx->dev;
> +	struct dma2d_fmt *fmt;
> +	enum v4l2_field *field;
> +	u32 fourcc = f->fmt.pix.pixelformat;
> +
> +	fmt = find_fmt(fourcc);
> +	if (!fmt) {
> +		v4l2_warn(&dev->v4l2_dev,
> +			"Format not supported: %c%c%c%c, use the default.\n",
> +			(fourcc & 0xff),  (fourcc >>  8) & 0xff,
> +			(fourcc >> 16) & 0xff, (fourcc >> 24) & 0xff);
> +		f->fmt.pix.pixelformat = formats[0].fourcc;
> +		fmt = find_fmt(f->fmt.pix.pixelformat);
> +	}
> +
> +	field = &f->fmt.pix.field;
> +	if (*field == V4L2_FIELD_ANY)
> +		*field = V4L2_FIELD_NONE;
> +	else if (*field != V4L2_FIELD_NONE)
> +		return -EINVAL;
> +
> +	if (f->fmt.pix.width > MAX_WIDTH)
> +		f->fmt.pix.width = MAX_WIDTH;
> +	if (f->fmt.pix.height > MAX_HEIGHT)
> +		f->fmt.pix.height = MAX_HEIGHT;
> +
> +	if (f->fmt.pix.width < 1)
> +		f->fmt.pix.width = 1;
> +	if (f->fmt.pix.height < 1)
> +		f->fmt.pix.height = 1;
> +
> +	if (f->type == V4L2_BUF_TYPE_VIDEO_OUTPUT && !f->fmt.pix.colorspace)
> +		f->fmt.pix.colorspace = V4L2_COLORSPACE_REC709;
> +	else if (f->type == V4L2_BUF_TYPE_VIDEO_CAPTURE) {
> +		f->fmt.pix.colorspace	= ctx->colorspace;
> +		f->fmt.pix.xfer_func = ctx->xfer_func;
> +		f->fmt.pix.ycbcr_enc = ctx->ycbcr_enc;
> +		f->fmt.pix.quantization = ctx->quant;
> +	}
> +	f->fmt.pix.bytesperline = (f->fmt.pix.width * fmt->depth) >> 3;
> +	f->fmt.pix.sizeimage = f->fmt.pix.height * f->fmt.pix.bytesperline;
> +
> +	return 0;
> +}
> +
> +static int vidioc_s_fmt(struct file *file, void *prv, struct v4l2_format *f)
> +{
> +	struct dma2d_ctx *ctx = prv;
> +	struct dma2d_dev *dev = ctx->dev;
> +	struct vb2_queue *vq;
> +	struct dma2d_frame *frm;
> +	struct dma2d_fmt *fmt;
> +	int ret = 0;
> +
> +	/* Adjust all values accordingly to the hardware capabilities
> +	 * and chosen format.
> +	 */
> +	ret = vidioc_try_fmt(file, prv, f);
> +	if (ret)
> +		return ret;
> +
> +	vq = v4l2_m2m_get_vq(ctx->fh.m2m_ctx, f->type);
> +	if (vb2_is_busy(vq)) {
> +		v4l2_err(&dev->v4l2_dev, "queue (%d) bust\n", f->type);
> +		return -EBUSY;
> +	}
> +
> +	frm = get_frame(ctx, f->type);
> +	if (IS_ERR(frm))
> +		return PTR_ERR(frm);
> +
> +	fmt = find_fmt(f->fmt.pix.pixelformat);
> +	if (!fmt)
> +		return -EINVAL;
> +
> +	if (f->type == V4L2_BUF_TYPE_VIDEO_OUTPUT) {
> +		ctx->colorspace = f->fmt.pix.colorspace;
> +		ctx->xfer_func = f->fmt.pix.xfer_func;
> +		ctx->ycbcr_enc = f->fmt.pix.ycbcr_enc;
> +		ctx->quant = f->fmt.pix.quantization;
> +	}
> +
> +	frm->width	= f->fmt.pix.width;
> +	frm->height	= f->fmt.pix.height;
> +	frm->size	= f->fmt.pix.sizeimage;
> +	/* Reset crop settings */
> +	frm->o_width	= 0;
> +	frm->o_height	= 0;
> +	frm->c_width	= frm->width;
> +	frm->c_height	= frm->height;
> +	frm->right	= frm->width;
> +	frm->bottom	= frm->height;
> +	frm->fmt	= fmt;
> +	frm->line_ofs	= 0;
> +	if (f->fmt.win.global_alpha != 0) {
> +		frm->a_rgb[3] = f->fmt.win.global_alpha;
> +		frm->a_mode = DMA2D_ALPHA_MODE_REPLACE;
> +	}
> +
> +	return 0;
> +}
> +
> +static void device_run(void *prv)
> +{
> +	struct dma2d_ctx *ctx = prv;
> +	struct dma2d_dev *dev = ctx->dev;
> +	struct dma2d_frame *frm_out, *frm_cap;
> +	struct vb2_v4l2_buffer *src, *dst;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&dev->ctrl_lock, flags);
> +	dev->curr = ctx;
> +
> +	src = v4l2_m2m_next_src_buf(ctx->fh.m2m_ctx);
> +	dst = v4l2_m2m_next_dst_buf(ctx->fh.m2m_ctx);
> +	if (dst == NULL || src == NULL)
> +		goto end;
> +
> +	frm_cap = get_frame(ctx, V4L2_BUF_TYPE_VIDEO_CAPTURE);
> +	frm_out = get_frame(ctx, V4L2_BUF_TYPE_VIDEO_OUTPUT);
> +	if (!frm_cap || !frm_out)
> +		goto end;
> +
> +	src->sequence = frm_out->sequence++;
> +	dst->sequence = frm_cap->sequence++;
> +	v4l2_m2m_buf_copy_metadata(src, dst, true);
> +
> +	clk_enable(dev->gate);
> +
> +	dma2d_config_fg(dev, frm_out,
> +		vb2_dma_contig_plane_dma_addr(&src->vb2_buf, 0));
> +
> +	/* TODO: add M2M_BLEND handler here */
> +
> +	if (ctx->op_mode != DMA2D_MODE_R2M) {
> +		if (frm_out->fmt->fourcc == frm_cap->fmt->fourcc)
> +			ctx->op_mode = DMA2D_MODE_M2M;
> +		else
> +			ctx->op_mode = DMA2D_MODE_M2M_FPC;
> +	}
> +
> +	dma2d_config_out(dev, frm_cap,
> +			vb2_dma_contig_plane_dma_addr(&dst->vb2_buf, 0));
> +	dma2d_config_common(dev, ctx->op_mode, frm_cap->width, frm_cap->height);
> +
> +	dma2d_start(dev);
> +end:
> +	spin_unlock_irqrestore(&dev->ctrl_lock, flags);
> +}
> +
> +static irqreturn_t dma2d_isr(int irq, void *prv)
> +{
> +	struct dma2d_dev *dev = prv;
> +	struct dma2d_ctx *ctx = dev->curr;
> +	struct vb2_v4l2_buffer *src, *dst;
> +	uint32_t s = dma2d_get_int(dev);
> +
> +	if (s & ISR_TCIF || s == 0) {
> +		dma2d_clear_int(dev);
> +		clk_disable(dev->gate);
> +
> +		WARN_ON(ctx == NULL);
> +
> +		src = v4l2_m2m_src_buf_remove(ctx->fh.m2m_ctx);
> +		dst = v4l2_m2m_dst_buf_remove(ctx->fh.m2m_ctx);
> +
> +		WARN_ON(dst == NULL);
> +		WARN_ON(src == NULL);
> +
> +		v4l2_m2m_buf_done(src, VB2_BUF_STATE_DONE);
> +		v4l2_m2m_buf_done(dst, VB2_BUF_STATE_DONE);
> +		v4l2_m2m_job_finish(dev->m2m_dev, ctx->fh.m2m_ctx);
> +
> +		dev->curr = NULL;
> +	} else {
> +		dma2d_clear_int(dev);
> +	}
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static const struct v4l2_file_operations dma2d_fops = {
> +	.owner		= THIS_MODULE,
> +	.open		= dma2d_open,
> +	.release	= dma2d_release,
> +	.poll		= v4l2_m2m_fop_poll,
> +	.unlocked_ioctl	= video_ioctl2,
> +	.mmap		= v4l2_m2m_fop_mmap,
> +#ifndef CONFIG_MMU
> +	.get_unmapped_area = v4l2_m2m_get_unmapped_area,
> +#endif
> +};
> +
> +static const struct v4l2_ioctl_ops dma2d_ioctl_ops = {
> +	.vidioc_querycap	= vidioc_querycap,
> +
> +	.vidioc_enum_fmt_vid_cap	= vidioc_enum_fmt,
> +	.vidioc_g_fmt_vid_cap		= vidioc_g_fmt,
> +	.vidioc_try_fmt_vid_cap		= vidioc_try_fmt,
> +	.vidioc_s_fmt_vid_cap		= vidioc_s_fmt,
> +
> +	.vidioc_enum_fmt_vid_out	= vidioc_enum_fmt,
> +	.vidioc_g_fmt_vid_out		= vidioc_g_fmt,
> +	.vidioc_try_fmt_vid_out		= vidioc_try_fmt,
> +	.vidioc_s_fmt_vid_out		= vidioc_s_fmt,
> +
> +	.vidioc_reqbufs			= v4l2_m2m_ioctl_reqbufs,
> +	.vidioc_querybuf		= v4l2_m2m_ioctl_querybuf,
> +	.vidioc_qbuf			= v4l2_m2m_ioctl_qbuf,
> +	.vidioc_dqbuf			= v4l2_m2m_ioctl_dqbuf,
> +	.vidioc_prepare_buf		= v4l2_m2m_ioctl_prepare_buf,
> +	.vidioc_create_bufs		= v4l2_m2m_ioctl_create_bufs,
> +	.vidioc_expbuf			= v4l2_m2m_ioctl_expbuf,
> +
> +	.vidioc_streamon		= v4l2_m2m_ioctl_streamon,
> +	.vidioc_streamoff		= v4l2_m2m_ioctl_streamoff,
> +
> +	.vidioc_subscribe_event = v4l2_ctrl_subscribe_event,
> +	.vidioc_unsubscribe_event = v4l2_event_unsubscribe,
> +};
> +
> +static const struct video_device dma2d_videodev = {
> +	.name		= DMA2D_NAME,
> +	.fops		= &dma2d_fops,
> +	.ioctl_ops	= &dma2d_ioctl_ops,
> +	.minor		= -1,
> +	.release	= video_device_release,
> +	.vfl_dir	= VFL_DIR_M2M,
> +};
> +
> +static const struct v4l2_m2m_ops dma2d_m2m_ops = {
> +	.device_run	= device_run,
> +};
> +
> +static const struct of_device_id stm32_dma2d_match[];
> +
> +static int dma2d_probe(struct platform_device *pdev)
> +{
> +	struct dma2d_dev *dev;
> +	struct video_device *vfd;
> +	struct resource *res;
> +	int ret = 0;
> +
> +	dev = devm_kzalloc(&pdev->dev, sizeof(*dev), GFP_KERNEL);
> +	if (!dev)
> +		return -ENOMEM;
> +
> +	spin_lock_init(&dev->ctrl_lock);
> +	mutex_init(&dev->mutex);
> +	atomic_set(&dev->num_inst, 0);
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +
> +	dev->regs = devm_ioremap_resource(&pdev->dev, res);
> +	if (IS_ERR(dev->regs))
> +		return PTR_ERR(dev->regs);
> +
> +	dev->gate = clk_get(&pdev->dev, "dma2d");
> +	if (IS_ERR(dev->gate)) {
> +		dev_err(&pdev->dev, "failed to get dma2d clock gate\n");
> +		ret = -ENXIO;
> +		return ret;
> +	}
> +
> +	ret = clk_prepare(dev->gate);
> +	if (ret) {
> +		dev_err(&pdev->dev, "failed to prepare dma2d clock gate\n");
> +		goto put_clk_gate;
> +	}
> +
> +	res = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
> +	if (!res) {
> +		dev_err(&pdev->dev, "failed to find IRQ\n");
> +		ret = -ENXIO;
> +		goto unprep_clk_gate;
> +	}
> +
> +	dev->irq = res->start;
> +
> +	ret = devm_request_irq(&pdev->dev, dev->irq, dma2d_isr,
> +						0, pdev->name, dev);
> +	if (ret) {
> +		dev_err(&pdev->dev, "failed to install IRQ\n");
> +		goto unprep_clk_gate;
> +	}
> +
> +	ret = v4l2_device_register(&pdev->dev, &dev->v4l2_dev);
> +	if (ret)
> +		goto unprep_clk_gate;
> +
> +	vfd = video_device_alloc();
> +	if (!vfd) {
> +		v4l2_err(&dev->v4l2_dev, "Failed to allocate video device\n");
> +		ret = -ENOMEM;
> +		goto unreg_v4l2_dev;
> +	}
> +
> +	*vfd = dma2d_videodev;
> +	set_bit(V4L2_FL_QUIRK_INVERTED_CROP, &vfd->flags);
> +	vfd->lock = &dev->mutex;
> +	vfd->v4l2_dev = &dev->v4l2_dev;
> +	vfd->device_caps = V4L2_CAP_VIDEO_M2M | V4L2_CAP_STREAMING;
> +	ret = video_register_device(vfd, VFL_TYPE_VIDEO, 0);
> +	if (ret) {
> +		v4l2_err(&dev->v4l2_dev, "Failed to register video device\n");
> +		goto rel_vdev;
> +	}
> +
> +	video_set_drvdata(vfd, dev);
> +	dev->vfd = vfd;
> +	v4l2_info(&dev->v4l2_dev, "device registered as /dev/video%d\n",
> +								vfd->num);
> +	platform_set_drvdata(pdev, dev);
> +	dev->m2m_dev = v4l2_m2m_init(&dma2d_m2m_ops);
> +	if (IS_ERR(dev->m2m_dev)) {
> +		v4l2_err(&dev->v4l2_dev, "Failed to init mem2mem device\n");
> +		ret = PTR_ERR(dev->m2m_dev);
> +		goto unreg_video_dev;
> +	}
> +
> +	v4l2_info(&dev->v4l2_dev, "stm32 dma2d initialized\n");
> +	return 0;
> +
> +unreg_video_dev:
> +	video_unregister_device(dev->vfd);
> +rel_vdev:
> +	video_device_release(vfd);
> +unreg_v4l2_dev:
> +	v4l2_device_unregister(&dev->v4l2_dev);
> +unprep_clk_gate:
> +	clk_unprepare(dev->gate);
> +put_clk_gate:
> +	clk_put(dev->gate);
> +
> +	return ret;
> +}
> +
> +static int dma2d_remove(struct platform_device *pdev)
> +{
> +	struct dma2d_dev *dev = platform_get_drvdata(pdev);
> +
> +	v4l2_info(&dev->v4l2_dev, "Removing " DMA2D_NAME);
> +	v4l2_m2m_release(dev->m2m_dev);
> +	video_unregister_device(dev->vfd);
> +	v4l2_device_unregister(&dev->v4l2_dev);
> +	vb2_dma_contig_clear_max_seg_size(&pdev->dev);
> +	clk_unprepare(dev->gate);
> +	clk_put(dev->gate);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id stm32_dma2d_match[] = {
> +	{
> +		.compatible = "st,stm32-dma2d",
> +		.data = NULL,
> +	},
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, stm32_dma2d_match);
> +
> +static struct platform_driver dma2d_pdrv = {
> +	.probe		= dma2d_probe,
> +	.remove		= dma2d_remove,
> +	.driver		= {
> +		.name = DMA2D_NAME,
> +		.of_match_table = stm32_dma2d_match,
> +	},
> +};
> +
> +module_platform_driver(dma2d_pdrv);
> +
> +MODULE_AUTHOR("Dillon Min <dillon.minfei@gmail.com>");
> +MODULE_DESCRIPTION("STM32 Chrom-Art Accelerator DMA2D driver");
> +MODULE_LICENSE("GPL");
> diff --git a/drivers/media/platform/stm32/dma2d/dma2d.h b/drivers/media/platform/stm32/dma2d/dma2d.h
> new file mode 100644
> index 000000000000..1c64cd2f7587
> --- /dev/null
> +++ b/drivers/media/platform/stm32/dma2d/dma2d.h
> @@ -0,0 +1,132 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +/*
> + * ST stm32 DMA2D - 2D Graphics Accelerator Driver
> + *
> + * Copyright (c) 2021 Dillon Min
> + * Dillon Min, <dillon.minfei@gmail.com>
> + *
> + * based on s5p-g2d
> + *
> + * Copyright (c) 2011 Samsung Electronics Co., Ltd.
> + * Kamil Debski, <k.debski@samsung.com>
> + */
> +
> +#ifndef __DMA2D_H__
> +#define __DMA2D_H__
> +
> +#include <linux/platform_device.h>
> +#include <media/v4l2-device.h>
> +#include <media/v4l2-ctrls.h>
> +
> +#define DMA2D_NAME "stm-dma2d"
> +#define BUS_INFO "platform:stm-dma2d"
> +enum dma2d_op_mode {
> +	DMA2D_MODE_M2M,
> +	DMA2D_MODE_M2M_FPC,
> +	DMA2D_MODE_M2M_BLEND,
> +	DMA2D_MODE_R2M
> +};
> +
> +enum dma2d_cmode {
> +	/* output pfc cmode from ARGB888 to ARGB4444 */
> +	DMA2D_CMODE_ARGB8888,
> +	DMA2D_CMODE_RGB888,
> +	DMA2D_CMODE_RGB565,
> +	DMA2D_CMODE_ARGB1555,
> +	DMA2D_CMODE_ARGB4444,
> +	/* bg or fg pfc cmode from L8 to A4 */
> +	DMA2D_CMODE_L8,
> +	DMA2D_CMODE_AL44,
> +	DMA2D_CMODE_AL88,
> +	DMA2D_CMODE_L4,
> +	DMA2D_CMODE_A8,
> +	DMA2D_CMODE_A4
> +};
> +
> +enum dma2d_alpha_mode {
> +	DMA2D_ALPHA_MODE_NO_MODIF,
> +	DMA2D_ALPHA_MODE_REPLACE,
> +	DMA2D_ALPHA_MODE_COMBINE
> +};
> +
> +struct dma2d_fmt {
> +	u32	fourcc;
> +	int	depth;
> +	enum dma2d_cmode cmode;
> +};
> +
> +struct dma2d_frame {
> +	/* Original dimensions */
> +	u32	width;
> +	u32	height;
> +	/* Crop size */
> +	u32	c_width;
> +	u32	c_height;
> +	/* Offset */
> +	u32	o_width;
> +	u32	o_height;
> +	u32	bottom;
> +	u32	right;
> +	u16	line_ofs;
> +	/* Image format */
> +	struct dma2d_fmt *fmt;
> +	/* [0]: blue
> +	 * [1]: green
> +	 * [2]: red
> +	 * [3]: alpha
> +	 */
> +	u8	a_rgb[4];
> +	/*
> +	 * AM[1:0] of DMA2D_FGPFCCR
> +	 */
> +	enum dma2d_alpha_mode a_mode;
> +	u32 size;
> +	unsigned int	sequence;
> +};
> +
> +struct dma2d_ctx {
> +	struct v4l2_fh fh;
> +	struct dma2d_dev	*dev;
> +	struct dma2d_frame	fg;
> +	struct dma2d_frame	out;
> +	struct dma2d_frame	bg;
> +	/* fb_buf always point to bg address */
> +	struct v4l2_framebuffer	fb_buf;
> +	/*
> +	 * MODE[17:16] of DMA2D_CR
> +	 */
> +	enum dma2d_op_mode	op_mode;
> +	u8			alpha_component;
> +	struct v4l2_ctrl_handler ctrl_handler;
> +	enum v4l2_colorspace	colorspace;
> +	enum v4l2_ycbcr_encoding ycbcr_enc;
> +	enum v4l2_xfer_func	xfer_func;
> +	enum v4l2_quantization	quant;
> +};
> +
> +struct dma2d_dev {
> +	struct v4l2_device	v4l2_dev;
> +	struct v4l2_m2m_dev	*m2m_dev;
> +	struct video_device	*vfd;
> +	struct mutex		mutex;
> +	spinlock_t		ctrl_lock;
> +	atomic_t		num_inst;
> +	void __iomem		*regs;
> +	struct clk		*gate;
> +	struct dma2d_ctx	*curr;
> +	int irq;
> +};
> +
> +void dma2d_start(struct dma2d_dev *d);
> +u32 dma2d_get_int(struct dma2d_dev *d);
> +void dma2d_clear_int(struct dma2d_dev *d);
> +void dma2d_config_out(struct dma2d_dev *d, struct dma2d_frame *frm,
> +			dma_addr_t o_addr);
> +void dma2d_config_fg(struct dma2d_dev *d, struct dma2d_frame *frm,
> +		dma_addr_t f_addr);
> +void dma2d_config_bg(struct dma2d_dev *d, struct dma2d_frame *frm,
> +		dma_addr_t b_addr);
> +void dma2d_config_common(struct dma2d_dev *d, enum dma2d_op_mode op_mode,
> +		u16 width, u16 height);
> +
> +#endif /* __DMA2D_H__ */
> 

Regards,

	Hans