Hi Sakari, On Wed, Aug 29, 2018 at 02:07:21PM +0300, Sakari Ailus wrote: > Hi Philippe, > > On Tue, Aug 28, 2018 at 06:02:55PM +0200, Philippe De Muyter wrote: > > Hi Hans, Sakari and Luca > > > > On Tue, Aug 28, 2018 at 11:22:28AM +0200, Hans Verkuil wrote: > > > On 26/08/18 22:41, Luca Ceresoli wrote: > > > > Hi Sakari, > > > > > > > > On 25/08/2018 16:49, Sakari Ailus wrote: > > > >> Hi Luca, > > > >> > > > >> On Fri, Aug 24, 2018 at 06:35:21PM +0200, Luca Ceresoli wrote: > > > >>> Forcibly setting the subdev name to DRIVER_NAME (i.e. "IMX274") makes > > > >>> it non-unique and less informative. > > > >>> > > > >>> Let the driver use the default name from i2c, e.g. "IMX274 2-001a". > > > >>> > > > >>> Signed-off-by: Luca Ceresoli <luca@xxxxxxxxxxxxxxxx> > > > >>> --- > > > >>> drivers/media/i2c/imx274.c | 1 - > > > >>> 1 file changed, 1 deletion(-) > > > >>> > > > >>> diff --git a/drivers/media/i2c/imx274.c b/drivers/media/i2c/imx274.c > > > >>> index 9b524de08470..570706695ca7 100644 > > > >>> --- a/drivers/media/i2c/imx274.c > > > >>> +++ b/drivers/media/i2c/imx274.c > > > >>> @@ -1885,7 +1885,6 @@ static int imx274_probe(struct i2c_client *client, > > > >>> imx274->client = client; > > > >>> sd = &imx274->sd; > > > >>> v4l2_i2c_subdev_init(sd, client, &imx274_subdev_ops); > > > >>> - strlcpy(sd->name, DRIVER_NAME, sizeof(sd->name)); > > > >>> sd->flags |= V4L2_SUBDEV_FL_HAS_DEVNODE | V4L2_SUBDEV_FL_HAS_EVENTS; > > > >>> > > > >>> /* initialize subdev media pad */ > > > >> > > > >> This ends up changing the entity as well as the sub-device name which may > > > >> well break applications. > > > > > > > > Right, unfortunately. > > > > > > > >> On the other hand, you currently can't have more > > > >> than one of these devices on a media device complex due to the name being > > > >> specific to a driver, not the device. > > > >> > > > >> An option avoiding that would be to let the user choose by e.g. through a > > > >> Kconfig option would avoid having to address that, but I really hate adding > > > >> such options. > > > > > > > > I agree adding a Kconfig option just for this would be very annoying. > > > > However I think the issue affects a few other drivers (sr030pc30.c and > > > > s5c73m3-core.c apparently), thus maybe one option could serve them all. > > > > > > > >> I wonder what others think. If anyone ever needs to add another on a board > > > >> so that it ends up being the part of the same media device complex > > > >> (likely), then changing the name now rather than later would be the least > > > >> pain. In this case I'd be leaning (slightly) towards accepting the patch > > > >> and hoping there wouldn't be any fallout... I don't see any board (DT) > > > >> containing imx274, at least not in the upstream kernel. > > > > > > > > I'll be OK with either decision. Should we keep it as is, then I think a > > > > comment before that line would be appropriate to clarify it's not > > > > correct but it is kept for backward userspace compatibility. This would > > > > help avoid new driver writers doing the same mistake, and prevent other > > > > people to send another patch like mine. > > > > > > In this end, this is a driver bug. I would just fix this, but add a comment > > > that states the old name and why it was changed. No need for a dev_info > > > IMHO. > > > > > > It would be nice if you can check if the same mistake is made in other drivers, > > > and update those as well. It's easier if this is all done at the same time. > > > > > > > Then we should probably also apply the following patch I submitted : > > > > "media: v4l2-common: v4l2_spi_subdev_init : generate unique name" > > https://patchwork.kernel.org/patch/10553035/ > > > > and perhaps > > > > "media: v4l2-common: simplify v4l2_i2c_subdev_init name generation" > > https://patchwork.kernel.org/patch/10553037/ > > The problem with this patch is that the existing naming scheme is very > similar while the new one offers no tangible benefits apart from being in > line with the rest of the kernel. That's still not a benefit for uAPI: > changing the name is certain to break user space applications. I agree with you on the patch for v4l2_i2c_subdev_init (I wrote 'perhaps'), but you don't say anything on the one about v4l2_spi_subdev_init :), which fixes an actual bug. I have 2 identical SPI-controlled sensors on the same board, and without my patch they get the same subdev name. Of course, I could fix that in the sensor driver itself, but that's not what we want, or do we ? Best Regards Philippe -- Philippe De Muyter +32 2 6101532 Macq SA rue de l'Aeronef 2 B-1140 Bruxelles
