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Subject: Re: [PATCH v8 3/5] staging: bcm2835-camera: Register bcm2835-camera with vchiq_bus_type
From:   Kieran Bingham <kieran.bingham@ideasonboard.com>
Cc:     stefan.wahren@i2se.com, gregkh@linuxfoundation.org,
        f.fainelli@gmail.com, athierry@redhat.com, error27@gmail.com,
        dave.stevenson@raspberrypi.com, laurent.pinchart@ideasonboard.com,
        Umang Jain <umang.jain@ideasonboard.com>
To:     Umang Jain <umang.jain@ideasonboard.com>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-media@vger.kernel.org, linux-rpi-kernel@lists.infradead.org,
        linux-staging@lists.linux.dev
Date:   Wed, 28 Jun 2023 23:44:31 +0100
Message-ID: <168799227183.3298351.12365161998104715465@Monstersaurus>
User-Agent: alot/0.10
Precedence: bulk

Quoting Umang Jain (2023-06-27 21:16:26)
> Register the bcm2835-camera with the vchiq_bus_type instead of using
> platform driver/device.
>=20
> Also the VCHIQ firmware doesn't support device enumeration, hence
> one has to maintain a list of devices to be registered in the interface.
>=20
> Signed-off-by: Umang Jain <umang.jain@ideasonboard.com>
> ---
>  .../bcm2835-camera/bcm2835-camera.c           | 16 +++++++-------
>  .../interface/vchiq_arm/vchiq_arm.c           | 21 ++++++++++++++++---
>  2 files changed, 26 insertions(+), 11 deletions(-)
>=20
> diff --git a/drivers/staging/vc04_services/bcm2835-camera/bcm2835-camera.=
c b/drivers/staging/vc04_services/bcm2835-camera/bcm2835-camera.c
> index 346d00df815a..f37b2a881d92 100644
> --- a/drivers/staging/vc04_services/bcm2835-camera/bcm2835-camera.c
> +++ b/drivers/staging/vc04_services/bcm2835-camera/bcm2835-camera.c
> @@ -24,8 +24,9 @@
>  #include <media/v4l2-event.h>
>  #include <media/v4l2-common.h>
>  #include <linux/delay.h>
> -#include <linux/platform_device.h>
> =20
> +#include "../interface/vchiq_arm/vchiq_arm.h"
> +#include "../interface/vchiq_arm/vchiq_device.h"
>  #include "../vchiq-mmal/mmal-common.h"
>  #include "../vchiq-mmal/mmal-encodings.h"
>  #include "../vchiq-mmal/mmal-vchiq.h"
> @@ -1841,7 +1842,7 @@ static struct v4l2_format default_v4l2_format =3D {
>         .fmt.pix.sizeimage =3D 1024 * 768,
>  };
> =20
> -static int bcm2835_mmal_probe(struct platform_device *pdev)
> +static int bcm2835_mmal_probe(struct vchiq_device *device)
>  {
>         int ret;
>         struct bcm2835_mmal_dev *dev;
> @@ -1896,7 +1897,7 @@ static int bcm2835_mmal_probe(struct platform_devic=
e *pdev)
>                                                        &camera_instance);
>                 ret =3D v4l2_device_register(NULL, &dev->v4l2_dev);
>                 if (ret) {
> -                       dev_err(&pdev->dev, "%s: could not register V4L2 =
device: %d\n",
> +                       dev_err(&device->dev, "%s: could not register V4L=
2 device: %d\n",
>                                 __func__, ret);
>                         goto free_dev;
>                 }
> @@ -1976,7 +1977,7 @@ static int bcm2835_mmal_probe(struct platform_devic=
e *pdev)
>         return ret;
>  }
> =20
> -static void bcm2835_mmal_remove(struct platform_device *pdev)
> +static void bcm2835_mmal_remove(struct vchiq_device *device)
>  {
>         int camera;
>         struct vchiq_mmal_instance *instance =3D gdev[0]->instance;
> @@ -1988,17 +1989,16 @@ static void bcm2835_mmal_remove(struct platform_d=
evice *pdev)
>         vchiq_mmal_finalise(instance);
>  }
> =20
> -static struct platform_driver bcm2835_camera_driver =3D {
> +static struct vchiq_driver bcm2835_camera_driver =3D {
>         .probe          =3D bcm2835_mmal_probe,
> -       .remove_new     =3D bcm2835_mmal_remove,
> +       .remove         =3D bcm2835_mmal_remove,
>         .driver         =3D {
>                 .name   =3D "bcm2835-camera",
>         },
>  };
> =20
> -module_platform_driver(bcm2835_camera_driver)
> +module_vchiq_driver(bcm2835_camera_driver)
> =20
>  MODULE_DESCRIPTION("Broadcom 2835 MMAL video capture");
>  MODULE_AUTHOR("Vincent Sanders");
>  MODULE_LICENSE("GPL");
> -MODULE_ALIAS("platform:bcm2835-camera");

This bit worries me. I think that's how module autoloading is handled.

Can you check into the details of MODULE_ALIAS and follow the rabbit
hole for a bit? It's a few years since I last went down there so I can't
remember the specifics right now.

Except for that, I think this looks good.


> diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.=
c b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
> index e8d40f891449..79d4d0eeb5fb 100644
> --- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
> +++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
> @@ -67,7 +67,6 @@ int vchiq_susp_log_level =3D VCHIQ_LOG_ERROR;
>  DEFINE_SPINLOCK(msg_queue_spinlock);
>  struct vchiq_state g_state;
> =20
> -static struct platform_device *bcm2835_camera;
>  static struct platform_device *bcm2835_audio;
> =20
>  struct vchiq_drvdata {
> @@ -134,6 +133,15 @@ struct vchiq_pagelist_info {
>         unsigned int scatterlist_mapped;
>  };
> =20
> +/*
> + * The devices implemented in the VCHIQ firmware are not discoverable,
> + * so we need to maintain a list of them in order to register them with
> + * the interface.
> + */
> +static const char *const vchiq_devices[] =3D {
> +       "bcm2835-camera",
> +};
> +
>  static void __iomem *g_regs;
>  /* This value is the size of the L2 cache lines as understood by the
>   * VPU firmware, which determines the required alignment of the
> @@ -1798,6 +1806,7 @@ static int vchiq_probe(struct platform_device *pdev)
>         struct device_node *fw_node;
>         const struct of_device_id *of_id;
>         struct vchiq_drvdata *drvdata;
> +       unsigned int i;
>         int err;
> =20
>         of_id =3D of_match_node(vchiq_of_match, pdev->dev.of_node);
> @@ -1840,9 +1849,15 @@ static int vchiq_probe(struct platform_device *pde=
v)
>                 goto error_exit;
>         }
> =20
> -       bcm2835_camera =3D vchiq_register_child(pdev, "bcm2835-camera");
>         bcm2835_audio =3D vchiq_register_child(pdev, "bcm2835_audio");
> =20
> +       for (i =3D 0; i < ARRAY_SIZE(vchiq_devices); i++) {
> +               err =3D vchiq_device_register(&pdev->dev, vchiq_devices[i=
]);
> +               if (err)
> +                       dev_err(&pdev->dev, "Failed to register %s vchiq =
device\n",
> +                       vchiq_devices[i]);
> +       }
> +
>         return 0;
> =20
>  failed_platform_init:
> @@ -1854,7 +1869,7 @@ static int vchiq_probe(struct platform_device *pdev)
>  static void vchiq_remove(struct platform_device *pdev)
>  {
>         platform_device_unregister(bcm2835_audio);
> -       platform_device_unregister(bcm2835_camera);
> +       bus_for_each_dev(&vchiq_bus_type, NULL, NULL, vchiq_device_unregi=
ster);
>         vchiq_debugfs_deinit();
>         vchiq_deregister_chrdev();
>  }
> --=20
> 2.39.1
>