Re: [PATCH v12 5/6] staging: bcm2835-camera: Register bcm2835-camera with vchiq_bus_type

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Mon, Oct 09, 2023 at 09:50:29AM +0530, Umang Jain wrote:
> Hi Greg,
> 
> Sorry for late reply, as I was traveling and then was on vacation for rest
> of the week.
> 
> On 10/5/23 1:34 PM, Greg Kroah-Hartman wrote:
> > On Sat, Sep 23, 2023 at 08:01:59PM +0530, Umang Jain wrote:
> > > Register the bcm2835-camera with the vchiq_bus_type instead of using
> > > platform driver/device.
> > > 
> > > Since we moved away bcm2835-camera from platform driver/device,
> > > we have to set the DMA mask explicitly. Set the DMA mask at probe
> > > time.
> > > 
> > > Also the VCHIQ firmware doesn't support device enumeration, hence
> > > one has to maintain a list of devices to be registered in the interface.
> > > 
> > > Signed-off-by: Umang Jain <umang.jain@ideasonboard.com>
> > > ---
> > >   .../bcm2835-camera/bcm2835-camera.c           | 21 ++++++++++---------
> > >   .../interface/vchiq_arm/vchiq_arm.c           | 11 +++++++---
> > >   2 files changed, 19 insertions(+), 13 deletions(-)
> > > 
> > > diff --git a/drivers/staging/vc04_services/bcm2835-camera/bcm2835-camera.c b/drivers/staging/vc04_services/bcm2835-camera/bcm2835-camera.c
> > > index fcad5118f3e8..c873eace1437 100644
> > > --- a/drivers/staging/vc04_services/bcm2835-camera/bcm2835-camera.c
> > > +++ b/drivers/staging/vc04_services/bcm2835-camera/bcm2835-camera.c
> > > @@ -11,6 +11,7 @@
> > >    *          Luke Diamand @ Broadcom
> > >    */
> > > +#include <linux/dma-mapping.h>
> > >   #include <linux/errno.h>
> > >   #include <linux/kernel.h>
> > >   #include <linux/module.h>
> > > @@ -24,8 +25,8 @@
> > >   #include <media/v4l2-event.h>
> > >   #include <media/v4l2-common.h>
> > >   #include <linux/delay.h>
> > > -#include <linux/platform_device.h>
> > > +#include "../interface/vchiq_arm/vchiq_bus.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 = {
> > >   	.fmt.pix.sizeimage = 1024 * 768,
> > >   };
> > > -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;
> > > @@ -1852,9 +1853,9 @@ static int bcm2835_mmal_probe(struct platform_device *pdev)
> > >   	unsigned int resolutions[MAX_BCM2835_CAMERAS][2];
> > >   	int i;
> > > -	ret = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32));
> > > +	ret = dma_set_mask_and_coherent(&device->dev, DMA_BIT_MASK(32));
> > >   	if (ret) {
> > > -		dev_err(&pdev->dev, "dma_set_mask_and_coherent failed: %d\n", ret);
> > > +		dev_err(&device->dev, "dma_set_mask_and_coherent failed: %d\n", ret);
> > >   		return ret;
> > >   	}
> > > @@ -1902,7 +1903,7 @@ static int bcm2835_mmal_probe(struct platform_device *pdev)
> > >   						       &camera_instance);
> > >   		ret = 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 V4L2 device: %d\n",
> > >   				__func__, ret);
> > >   			goto free_dev;
> > >   		}
> > > @@ -1982,7 +1983,7 @@ static int bcm2835_mmal_probe(struct platform_device *pdev)
> > >   	return ret;
> > >   }
> > > -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 = gdev[0]->instance;
> > > @@ -1994,17 +1995,17 @@ static void bcm2835_mmal_remove(struct platform_device *pdev)
> > >   	vchiq_mmal_finalise(instance);
> > >   }
> > > -static struct platform_driver bcm2835_camera_driver = {
> > > +static struct vchiq_driver bcm2835_camera_driver = {
> > >   	.probe		= bcm2835_mmal_probe,
> > > -	.remove_new	= bcm2835_mmal_remove,
> > > +	.remove		= bcm2835_mmal_remove,
> > >   	.driver		= {
> > >   		.name	= "bcm2835-camera",
> > >   	},
> > >   };
> > > -module_platform_driver(bcm2835_camera_driver)
> > > +module_vchiq_driver(bcm2835_camera_driver)
> > >   MODULE_DESCRIPTION("Broadcom 2835 MMAL video capture");
> > >   MODULE_AUTHOR("Vincent Sanders");
> > >   MODULE_LICENSE("GPL");
> > > -MODULE_ALIAS("platform:bcm2835-camera");
> > > +MODULE_ALIAS("bcm2835-camera");
> > Now that you are on your own bus, why do you need the MODULE_ALIAS()
> > line at all?
> 
> Because it breaks the module auto-loading support...

But that's not how auto-loading should work once you have a real bus.

> If you look at the vchiq_bus patch (3/6) in this series, there is
> vchiq_bus_uevent() which sends a event that includes the MODALIAS.

The module alias should be automatically picked out of the
MODULE_DEVICE_TABLE() macro that you should be using for this driver,
you should never have to manually create MODULE_ALIAS() lines.

That's a bad hold-over because the platform driver subsystem can not
handle module aliases on it's own, let's not copy that bad pattern here
as well please.

thanks,

greg k-h

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