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Message-ID: <ad04b435-87d4-8f15-e5b8-d9c8fd364024@zago.net>
Date:   Mon, 27 Jun 2022 18:30:06 -0500
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Subject: Re: [PATCH v6 1/4] mfd: ch341: add core driver for the WCH CH341 in
 I2C/SPI/GPIO mode
Content-Language: en-US
To:     Lee Jones <lee.jones@linaro.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc:     linux-kernel@vger.kernel.org,
        Bartosz Golaszewski <bgolaszewski@baylibre.com>,
        Wolfram Sang <wsa@kernel.org>, Johan Hovold <johan@kernel.org>,
        linux-usb@vger.kernel.org,
        Linus Walleij <linus.walleij@linaro.org>,
        linux-gpio@vger.kernel.org, linux-i2c@vger.kernel.org
References: <20220616013747.126051-1-frank@zago.net>
 <20220616013747.126051-2-frank@zago.net> <Yrm48AYxkmoUgdwr@google.com>
 <Yrm+kH6NvTy5A9WO@kroah.com> <YrnCBpvA8/y38Brg@google.com>
From:   Frank Zago <frank@zago.net>
In-Reply-To: <YrnCBpvA8/y38Brg@google.com>
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Precedence: bulk

On 6/27/22 09:43, Lee Jones wrote:
> On Mon, 27 Jun 2022, Greg Kroah-Hartman wrote:
> 
>> On Mon, Jun 27, 2022 at 03:04:32PM +0100, Lee Jones wrote:
>>> USB review please.
>>>
>>>> The CH341 is a multifunction chip, presenting 3 different USB PID. One
>>>>
>>>> of these functions is for I2C/SPI/GPIO. This new set of drivers will
>>>> manage I2C and GPIO.
>>>>
>>>> Signed-off-by: frank zago <frank@zago.net>
>>>> ---
>>>>  MAINTAINERS               |  7 +++
>>>>  drivers/mfd/Kconfig       | 10 +++++
>>>>  drivers/mfd/Makefile      |  1 +
>>>>  drivers/mfd/ch341-core.c  | 90 +++++++++++++++++++++++++++++++++++++++
>>>>  include/linux/mfd/ch341.h | 18 ++++++++
>>>>  5 files changed, 126 insertions(+)
>>>>  create mode 100644 drivers/mfd/ch341-core.c
>>>>  create mode 100644 include/linux/mfd/ch341.h
>>>>
>>>> diff --git a/MAINTAINERS b/MAINTAINERS
>>>> index 43d3d07afccd..628eeaa9bf68 100644
>>>> --- a/MAINTAINERS
>>>> +++ b/MAINTAINERS
>>>> @@ -21475,6 +21475,13 @@ M:	David Härdeman <david@hardeman.nu>
>>>>  S:	Maintained
>>>>  F:	drivers/media/rc/winbond-cir.c
>>>>  
>>>> +WINCHIPHEAD CH341 I2C/GPIO MFD DRIVER
>>>> +M:	Frank Zago <frank@zago.net>
>>>> +L:	linux-usb@vger.kernel.org
>>>> +S:	Maintained
>>>> +F:	drivers/mfd/ch341-core.c
>>>> +F:	include/linux/mfd/ch341.h
>>>> +
>>>>  WINSYSTEMS EBC-C384 WATCHDOG DRIVER
>>>>  M:	William Breathitt Gray <vilhelm.gray@gmail.com>
>>>>  L:	linux-watchdog@vger.kernel.org
>>>> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
>>>> index 3b59456f5545..893acc821a42 100644
>>>> --- a/drivers/mfd/Kconfig
>>>> +++ b/drivers/mfd/Kconfig
>>>> @@ -1784,6 +1784,16 @@ config MFD_LOCHNAGAR
>>>>  	help
>>>>  	  Support for Cirrus Logic Lochnagar audio development board.
>>>>  
>>>> +config MFD_CH341
>>>> +	tristate "WinChipHead CH341 in I2C/SPI/GPIO mode"
>>>> +	depends on USB
>>>> +	help
>>>> +	  If you say yes to this option, support for the CH341 series
>>>> +	  of chips, running in I2C/SPI/GPIO mode will be included.
>>>> +
>>>> +	  This driver can also be built as a module.  If so, the
>>>> +	  module will be called ch341-core.
>>>> +
>>>>  config MFD_ARIZONA
>>>>  	select REGMAP
>>>>  	select REGMAP_IRQ
>>>> diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
>>>> index 858cacf659d6..fd615ab3929f 100644
>>>> --- a/drivers/mfd/Makefile
>>>> +++ b/drivers/mfd/Makefile
>>>> @@ -13,6 +13,7 @@ obj-$(CONFIG_MFD_ASIC3)		+= asic3.o tmio_core.o
>>>>  obj-$(CONFIG_ARCH_BCM2835)	+= bcm2835-pm.o
>>>>  obj-$(CONFIG_MFD_BCM590XX)	+= bcm590xx.o
>>>>  obj-$(CONFIG_MFD_BD9571MWV)	+= bd9571mwv.o
>>>> +obj-$(CONFIG_MFD_CH341)		+= ch341-core.o
>>>>  obj-$(CONFIG_MFD_CROS_EC_DEV)	+= cros_ec_dev.o
>>>>  obj-$(CONFIG_MFD_ENE_KB3930)	+= ene-kb3930.o
>>>>  obj-$(CONFIG_MFD_EXYNOS_LPASS)	+= exynos-lpass.o
>>>> diff --git a/drivers/mfd/ch341-core.c b/drivers/mfd/ch341-core.c
>>>> new file mode 100644
>>>> index 000000000000..f08a67dd6074
>>>> --- /dev/null
>>>> +++ b/drivers/mfd/ch341-core.c
>>>> @@ -0,0 +1,90 @@
>>>> +// SPDX-License-Identifier: GPL-2.0
>>>> +/*
>>>> + * Core driver for the CH341A, CH341B and CH341T in I2C/SPI/GPIO
>>>> + * mode. There are cell drivers available for I2C and GPIO. SPI is not
>>>> + * yet supported.
>>>> + *
>>>> + * Copyright 2022, Frank Zago
>>>> + * Copyright (c) 2017 Gunar Schorcht (gunar@schorcht.net)
>>>> + * Copyright (c) 2016 Tse Lun Bien
>>>> + * Copyright (c) 2014 Marco Gittler
>>>> + * Copyright (c) 2006-2007 Till Harbaum (Till@Harbaum.org)
>>>> + */
>>>> +
>>>> +#include <linux/kernel.h>
>>>> +#include <linux/mfd/ch341.h>
>>>> +#include <linux/mfd/core.h>
>>>> +#include <linux/module.h>
>>>> +#include <linux/slab.h>
>>>> +#include <linux/usb.h>
>>>> +
>>>> +static const struct mfd_cell ch341_devs[] = {
>>>> +	{
>>>> +		.name = "ch341-gpio",
>>>> +	},
>>>> +	{
>>>> +		.name = "ch341-i2c",
>>>> +	},
>>>> +};
>>>> +
>>>> +static int ch341_usb_probe(struct usb_interface *iface,
>>>> +			   const struct usb_device_id *usb_id)
>>>> +{
>>>> +	struct usb_endpoint_descriptor *bulk_out;
>>>> +	struct usb_endpoint_descriptor *bulk_in;
>>>> +	struct usb_endpoint_descriptor *intr_in;
>>>> +	struct ch341_ddata *ddata;
>>>> +	int ret;
>>>> +
>>>> +	ddata = devm_kzalloc(&iface->dev, sizeof(*ddata), GFP_KERNEL);
>>>> +	if (!ddata)
>>>> +		return -ENOMEM;
>>>> +
>>>> +	ddata->usb_dev = interface_to_usbdev(iface);
>>>> +	mutex_init(&ddata->usb_lock);
>>>> +
>>>> +	ret = usb_find_common_endpoints(iface->cur_altsetting, &bulk_in,
>>>> +					&bulk_out, &intr_in, NULL);
>>>> +	if (ret) {
>>>> +		dev_err(&iface->dev, "Could not find all endpoints\n");
>>>> +		return -ENODEV;
>>>> +	}
>>>> +
>>>> +	ddata->ep_in = bulk_in->bEndpointAddress;
>>>> +	ddata->ep_out = bulk_out->bEndpointAddress;
>>>> +	ddata->ep_intr = intr_in->bEndpointAddress;
>>>> +	ddata->ep_intr_interval = intr_in->bInterval;
>>>> +
>>>> +	usb_set_intfdata(iface, ddata);
>>>> +
>>>> +	ret = mfd_add_devices(&iface->dev, PLATFORM_DEVID_AUTO, ch341_devs,
>>>> +			      ARRAY_SIZE(ch341_devs), NULL, 0, NULL);
>>>> +	if (ret)
>>>> +		return dev_err_probe(&iface->dev, ret,
>>>> +				     "Failed to register child devices\n");
>>>> +
>>>> +	return 0;
>>>> +}
>>>> +
>>>> +static void ch341_usb_disconnect(struct usb_interface *usb_if)
>>>> +{
>>>> +	mfd_remove_devices(&usb_if->dev);
>>>> +}
>>>> +
>>>> +static const struct usb_device_id ch341_usb_table[] = {
>>>> +	{ USB_DEVICE(0x1a86, 0x5512) },
>>>> +	{ }
>>>> +};
>>>> +MODULE_DEVICE_TABLE(usb, ch341_usb_table);
>>>> +
>>>> +static struct usb_driver ch341_usb_driver = {
>>>> +	.name       = "ch341-mfd",
>>>> +	.id_table   = ch341_usb_table,
>>>> +	.probe      = ch341_usb_probe,
>>>> +	.disconnect = ch341_usb_disconnect,
>>>> +};
>>>> +module_usb_driver(ch341_usb_driver);
>>>> +
>>>> +MODULE_AUTHOR("Frank Zago <frank@zago.net>");
>>>> +MODULE_DESCRIPTION("CH341 USB to I2C/SPI/GPIO adapter");
>>>> +MODULE_LICENSE("GPL");
>>>> diff --git a/include/linux/mfd/ch341.h b/include/linux/mfd/ch341.h
>>>> new file mode 100644
>>>> index 000000000000..44f5da0720bd
>>>> --- /dev/null
>>>> +++ b/include/linux/mfd/ch341.h
>>>> @@ -0,0 +1,18 @@
>>>> +/* SPDX-License-Identifier: GPL-2.0 */
>>>> +/* Definitions for the CH341 driver */
>>>> +
>>>> +#include <linux/mutex.h>
>>>> +#include <linux/types.h>
>>>> +
>>>> +struct usb_device;
>>>> +struct usb_interface;
>>>> +
>>>> +struct ch341_ddata {
>>>> +	struct usb_device *usb_dev;
>>>> +	struct mutex usb_lock;
>>>> +
>>>> +	int ep_in;
>>>> +	int ep_out;
>>>> +	int ep_intr;
>>>> +	u8 ep_intr_interval;
>>>> +};
>>
>>
>> Looks sane enough, but doesn't actually do any USB data transfers, maybe
>> that happens somewhere else...
> 
> I expect those to happen in *both* of these:
> 
>   static const struct mfd_cell ch341_devs[] = {
> 	{
> 		.name = "ch341-gpio",
> 	},
> 	{
> 		.name = "ch341-i2c",
> 	},
>   };
> 
> Is that correct Frank?

Yes, that's correct.

Frank