linux-kernel - Re: [PATCH 1/2] media: i2c: Add GC08A3 image sensor driver

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Date: Tue, 9 Jan 2024 11:23:08 +0000
From: "sakari.ailus@...ux.intel.com" <sakari.ailus@...ux.intel.com>
To: Zhi Mao (毛智) <zhi.mao@...iatek.com>
Cc: "heiko@...ech.de" <heiko@...ech.de>,
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Subject: Re: [PATCH 1/2] media: i2c: Add GC08A3 image sensor driver

Hi Zhi,

On Tue, Jan 09, 2024 at 10:41:15AM +0000, Zhi Mao (毛智) wrote:
> > > +static const char *const gc08a3_supply_name[] = {
> > > +"avdd",
> > > +"dvdd",
> > > +"dovdd",
> > > +};
> > > +
> > > +#define GC08A3_NUM_SUPPLIES ARRAY_SIZE(gc08a3_supply_name)
> > 
> > Please use ARRAY_SIZE(...) directly.
> > 
> [mtk]: About "ARRAY_SIZE", creating a macro with a descriptive name can
> improve readability of code, especially when it is used in multiple
> locations in codes. and it seems a common usage in sensor drivers. Can
> we keep this usage in gc08a3 driver?

It improves readability even more if you use ARRAY_SIZE() directly as then
it's easy to see you're dealing with a single array. GC08A3_NUM_SUPPLIES is
thus a useless definition.

..

> > > +static int gc08a3_g_mbus_config(struct v4l2_subdev *sd, unsigned
> > int pad,
> > > +struct v4l2_mbus_config *config)
> > > +{
> > > +config->type = V4L2_MBUS_CSI2_DPHY;
> > > +config->bus.mipi_csi2.num_data_lanes = 4;
> > > +config->bus.mipi_csi2.flags = 0;
> > > +return 0;
> > > +}
> > 
> > As you return a static configuration, there's no need to implement
> > g_mbus_config().
> > 
> [mtk]: we can not remove this function, because meidatek ISP driver
> will use this interface to get some information.

Please fix the Mediatek ISP driver in that case.

I'm also open to adding a V4L2 framework function to obtain the number of
lanes (and other configuration) for an upstream sub-device, either using
the local endpoint or g_mbus_config if the sub-device driver implements
that.

-- 
Regards,

Sakari Ailus