Re: [PATCH v3 3/5] media: hi846: fix modes handling for different lane cases

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
- [Low] The mode filtering logic for 4-lane setups relies on brittle array pointer arithmetic and implicitly assumes a specific global array ordering.
- [Low] A local variable shadows a global variable in `hi846_enum_frame_size`.
--

commit 809f6817858f4d273d756eeec1b017198bbcfa3a
Author: Pengyu Luo <mitltlatltl@gmail.com>

media: hi846: fix modes handling for different lane cases

When using 4-lane, a 640x480 mode may be incorrectly set. This patch fixes
the issue by specifying the supported modes and mode count dynamically based
on the number of lanes.

Closes: https://lore.kernel.org/linux-media/OmTXoHZJTSGePymL9I-1Cw@puri.sm/
Fixes: e8c0882685f9 ("media: i2c: add driver for the SK Hynix Hi-846 8M pixel camera")

> diff --git a/drivers/media/i2c/hi846.c b/drivers/media/i2c/hi846.c
> index befd54553df2e..9decfda747876 100644
> --- a/drivers/media/i2c/hi846.c
> +++ b/drivers/media/i2c/hi846.c

[ ... ]

> @@ -1821,8 +1825,11 @@ static int hi846_enum_frame_size(struct v4l2_subdev *sd,
>  				 struct v4l2_subdev_frame_size_enum *fse)
>  {
>  	struct i2c_client *client = v4l2_get_subdevdata(sd);
> +	struct hi846 *hi846 = to_hi846(sd);
> +	const struct hi846_mode *supported_modes = hi846->supported_modes;

This isn't a bug, but does declaring supported_modes here shadow the global
static array supported_modes[] defined earlier in the file?

[ ... ]

> @@ -1999,6 +2006,13 @@ static int hi846_parse_dt(struct hi846 *hi846, struct device *dev)
>  
>  	hi846->nr_lanes = bus_cfg.bus.mipi_csi2.num_data_lanes;
>  
> +	hi846->supported_modes = supported_modes;
> +	hi846->num_modes = NUM_MODES_2LANE;
> +	if (hi846->nr_lanes == 4) {
> +		hi846->supported_modes = supported_modes + 1;
> +		hi846->num_modes = NUM_MODES_4LANE;
> +	}

Does this mode filtering logic rely on the exact ordering of the global
supported_modes array?

By advancing the array pointer by 1 and using a hardcoded mode count for the
4-lane setup, this implicitly assumes the only mode incompatible with 4-lane
operation is located exactly at the first index.

If another 2-lane-only mode is added or the modes are reordered in the future,
could this silently corrupt the subdevice's mode list by misaligning the array
bounds?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260511090924.269106-1-mitltlatltl@gmail.com?part=3