[PATCH v2 1/2] media: mediatek: vcodec: Make decoder capability fields fit requirements

From: Chen-Yu Tsai
Date: Fri Jul 08 2022 - 06:45:37 EST

This partially reverts commit a8a7a278c56ad3b4ddd4db9a960e0537d032b0b3,
and changes things so that the capability string fields of the decoder
conform to their requirements.

This recent change caused ChromeOS's decoder to no longer function. This
is due to ChromeOS using the driver name field to match the video device
with its accompanying media device. After the change, they no longer

The driver name field should contain the actual driver name, not some
otherwise unused string macro from the driver. To make this clear,
copy the name from the driver's name field.

The card name for the video decoder previously held a static platform
name that was fixed to match MT8173. This obviously doesn't make sense
for newer chips. Since commit a8a7a278c56a ("media: mediatek: vcodec:
Change decoder v4l2 capability value"), this field was changed to hold
the driver's name, or "mtk-vcodec-dec". This doesn't make much sense
either, since this still doesn't reflect what chip this is.

Instead, fill in the card name with "MTxxxx video decoder" with the
proper chip number.

Since commit f2d8b6917f3b ("media: v4l: ioctl: Set bus_info in
v4l_querycap()"), the V4L2 core provides a default value for the
bus_info field for platform and PCI devices. This value will match
the default value for media devices added by commit cef699749f37
("media: mc: Set bus_info in media_device_init()"). These defaults
are stable and device-specific.

Drop the custom capability bus_info from the mtk-vcodec decoder
driver, and use the defaults. This also fixes the long standing
issue where the media device used for the stateless decoder didn't
have its bus_info set, and would never match its accompanying video

Fixes: a8a7a278c56a ("media: mediatek: vcodec: Change decoder v4l2 capability value")
Signed-off-by: Chen-Yu Tsai <wenst@xxxxxxxxxxxx>
drivers/media/platform/mediatek/vcodec/mtk_vcodec_dec.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/media/platform/mediatek/vcodec/mtk_vcodec_dec.c b/drivers/media/platform/mediatek/vcodec/mtk_vcodec_dec.c
index 5d6fdf18c3a6..209de1ec02e4 100644
--- a/drivers/media/platform/mediatek/vcodec/mtk_vcodec_dec.c
+++ b/drivers/media/platform/mediatek/vcodec/mtk_vcodec_dec.c
@@ -243,11 +243,12 @@ static int mtk_vcodec_dec_get_chip_name(void *priv)
static int vidioc_vdec_querycap(struct file *file, void *priv,
struct v4l2_capability *cap)
+ struct mtk_vcodec_ctx *ctx = fh_to_ctx(priv);
+ struct device *dev = &ctx->dev->plat_dev->dev;
int platform_name = mtk_vcodec_dec_get_chip_name(priv);

- strscpy(cap->driver, MTK_VCODEC_DRV_NAME, sizeof(cap->driver));
- strscpy(cap->card, MTK_VCODEC_DEC_NAME, sizeof(cap->card));
- snprintf(cap->bus_info, sizeof(cap->bus_info), "platform:mt%d-dec", platform_name);
+ strscpy(cap->driver, dev->driver->name, sizeof(cap->driver));
+ snprintf(cap->card, sizeof(cap->card), "MT%d video decoder", platform_name);

return 0;