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    SubjectRe: [PATCH 3/7] media: imx274: don't hard-code the subdev name to DRIVER_NAME
    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@lucaceresoli.net>
    > >>> ---
    > >>> 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/

    Philippe

    --
    Philippe De Muyter +32 2 6101532 Macq SA rue de l'Aeronef 2 B-1140 Bruxelles

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