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References: <20230627201628.207483-1-umang.jain@ideasonboard.com> <20230627201628.207483-4-umang.jain@ideasonboard.com> <168799227183.3298351.12365161998104715465@Monstersaurus> <2373ef89-4d93-d675-c050-4539a753a4d6@ideasonboard.com>
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
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:   Thu, 29 Jun 2023 13:19:47 +0100
Message-ID: <168804118770.3585053.4473096672239924197@Monstersaurus>
User-Agent: alot/0.10
Precedence: bulk

Quoting Umang Jain (2023-06-29 12:49:17)
> Hi Kieran,
>=20
> On 6/29/23 12:44 AM, Kieran Bingham wrote:
> > Quoting Umang Jain (2023-06-27 21:16:26)
> >> Register the bcm2835-camera with the vchiq_bus_type instead of using
> >> platform driver/device.
> >>
> >> Also the VCHIQ firmware doesn't support device enumeration, hence
> >> one has to maintain a list of devices to be registered in the interfac=
e.
> >>
> >> 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(-)
> >>
> >> diff --git a/drivers/staging/vc04_services/bcm2835-camera/bcm2835-came=
ra.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_de=
vice *pdev)
> >>                                                         &camera_instan=
ce);
> >>                  ret =3D v4l2_device_register(NULL, &dev->v4l2_dev);
> >>                  if (ret) {
> >> -                       dev_err(&pdev->dev, "%s: could not register V4=
L2 device: %d\n",
> >> +                       dev_err(&device->dev, "%s: could not register =
V4L2 device: %d\n",
> >>                                  __func__, ret);
> >>                          goto free_dev;
> >>                  }
> >> @@ -1976,7 +1977,7 @@ static int bcm2835_mmal_probe(struct platform_de=
vice *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 platfor=
m_device *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.
>=20
> vchiq_probe() will register both the bcm2385_audio and bcm2835-camera=20
> hence, we don't need MODULE_ALIAS for those two.

It registers the devices, but I thought MODULE_ALIAS was how that gets
tied to which module to load (when drivers are built as modules).

> So what I also tested is that, when bcm2835_vchiq loads, it will=20
> auto-load both audio and camera with it (since these are child devices=20
> of vchiq). I think that's the correct way.

Could you test a build with the following (two) configurations please?

1)
  CONFIG_BCM2835_VCHIQ=3Dy
  CONFIG_VIDEO_BCM2835=3Dm
  CONFIG_SND_BCM2835=3Dm

2)
  CONFIG_BCM2835_VCHIQ=3Dm
  CONFIG_VIDEO_BCM2835=3Dm
  CONFIG_SND_BCM2835=3Dm


> >
> > Except for that, I think this looks good.
> >
> >
> >> diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_a=
rm.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 wi=
th
> >> + * 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 *p=
dev)
> >>          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 *=
pdev)
> >>                  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_device=
s[i]);
> >> +               if (err)
> >> +                       dev_err(&pdev->dev, "Failed to register %s vch=
iq device\n",
> >> +                       vchiq_devices[i]);
> >> +       }
> >> +
> >>          return 0;
> >>  =20
> >>   failed_platform_init:
> >> @@ -1854,7 +1869,7 @@ static int vchiq_probe(struct platform_device *p=
dev)
> >>   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_unr=
egister);
> >>          vchiq_debugfs_deinit();
> >>          vchiq_deregister_chrdev();
> >>   }
> >> --=20
> >> 2.39.1
> >>
>