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Date:   Tue, 20 Jun 2023 13:09:34 +0200
From:   Tommaso Merciai <tomm.merciai@gmail.com>
To:     Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc:     Sakari Ailus <sakari.ailus@linux.intel.com>,
        jacopo.mondi@ideasonboard.com, martin.hecht@avnet.eu,
        michael.roeder@avnet.eu, linuxfancy@googlegroups.com,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Liam Girdwood <lgirdwood@gmail.com>,
        Mark Brown <broonie@kernel.org>,
        Hans Verkuil <hverkuil@xs4all.nl>,
        Marco Felsch <m.felsch@pengutronix.de>,
        Gerald Loacker <gerald.loacker@wolfvision.net>,
        Nicholas Roth <nicholas@rothemail.net>,
        Krzysztof =?utf-8?Q?Ha=C5=82asa?= <khalasa@piap.pl>,
        Linus Walleij <linus.walleij@linaro.org>,
        Benjamin Mugnier <benjamin.mugnier@foss.st.com>,
        Mikhail Rudenko <mike.rudenko@gmail.com>,
        Shawn Tu <shawnx.tu@intel.com>, linux-kernel@vger.kernel.org,
        linux-media@vger.kernel.org
Subject: Re: [PATCH v5 3/3] media: i2c: Add support for alvium camera
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Hi Laurent,

On Tue, Jun 20, 2023 at 01:53:35PM +0300, Laurent Pinchart wrote:
> Hi Tommaso,
> 
> On Tue, Jun 20, 2023 at 12:39:42PM +0200, Tommaso Merciai wrote:
> > On Tue, Jun 20, 2023 at 12:43:28PM +0300, Laurent Pinchart wrote:
> > > On Tue, Jun 20, 2023 at 06:54:43AM +0200, Tommaso Merciai wrote:
> > > > On Mon, Jun 19, 2023 at 05:24:58PM +0300, Laurent Pinchart wrote:
> > > > > On Mon, Jun 19, 2023 at 10:50:10AM +0000, Sakari Ailus wrote:
> > > > > > On Fri, Jun 09, 2023 at 03:09:41PM +0200, Tommaso Merciai wrote:
> > > > > > > On Fri, Jun 09, 2023 at 09:17:42AM +0000, Sakari Ailus wrote:
> > > > > > > > On Thu, Jun 08, 2023 at 10:31:16AM +0200, Tommaso Merciai wrote:
> > > > > > > > > The Alvium camera is shipped with sensor + isp in the same housing.
> > > > > > > > > The camera can be equipped with one out of various sensor and abstract
> > > > > > > > > the user from this. Camera is connected via MIPI CSI-2.
> > > > > > > > > 
> > > > > > > > > Most of the camera module features are supported, with the main exception
> > > > > > > > > being fw update.
> > > > > > > > > 
> > > > > > > > > The driver provides all mandatory, optional and recommended V4L2 controls
> > > > > > > > > for maximum compatibility with libcamera
> > > > > > > > > 
> > > > > > > > > References:
> > > > > > > > >  - https://www.alliedvision.com/en/products/embedded-vision-solutions
> > > > > > > > > 
> > > > > > > > > Signed-off-by: Tommaso Merciai <tomm.merciai@gmail.com>
> > > > > > > > > ---
> > > > > > > > > Changes since v2:
> > > > > > > > >  - Removed gpios/clock handling as suggested by LPinchart
> > > > > > > > >  - Added vcc-ext-in supply support as suggested by LPinchart
> > > > > > > > >  - Fixed alvium_setup_mipi_fmt funct as suggested by CJAILLET
> > > > > > > > >  - Removed upside_down/hshake_bit priv data as suggested by CJAILLET
> > > > > > > > >  - Fixed commit body as suggested by LPinchart
> > > > > > > > >  - Mv alvium_set_streamon_delay to yalvium_set_lp2hs_delay
> > > > > > > > >  - Fixed comment on lp2hs prop as suggested by LPinchart
> > > > > > > > >  - Added pm resume/suspend functs as suggested by LPinchart
> > > > > > > > >  - Dropped alvium_link_setup/alvium_s_power as suggested by LPinchart
> > > > > > > > >  - Fixed regs defines as suggested by LPinchart
> > > > > > > > >  - Fixed typedef as suggested by LPinchart
> > > > > > > > >  - Dropped bcrm_v/fw_v from priv data as suggested by LPinchart
> > > > > > > > >  - Now driver use the subdev active state to store the active format and crop
> > > > > > > > >    as suggested by LPinchart
> > > > > > > > >  - Dropped alvium_is_csi2/i2c_to_alvium as suggested by LPinchart
> > > > > > > > > 
> > > > > > > > > Changes since v3:
> > > > > > > > >  - Fixed warnings Reported-by: kernel test robot <lkp@intel.com>
> > > > > > > > > 
> > > > > > > > > Changes since v4:
> > > > > > > > >  - Removed print into alvium_get_dt_data for alliedvision,lp2hs-delay-us as
> > > > > > > > >    suggested by CDooley
> > > > > > > > > 
> > > > > > > > >  drivers/media/i2c/Kconfig       |   10 +
> > > > > > > > >  drivers/media/i2c/Makefile      |    1 +
> > > > > > > > >  drivers/media/i2c/alvium-csi2.c | 3479 +++++++++++++++++++++++++++++++
> > > > > > > > >  drivers/media/i2c/alvium-csi2.h |  485 +++++
> > > > > > > > >  4 files changed, 3975 insertions(+)
> > > > > > > > >  create mode 100644 drivers/media/i2c/alvium-csi2.c
> > > > > > > > >  create mode 100644 drivers/media/i2c/alvium-csi2.h
> > > > > 
> > > > > [snip]
> > > > > 
> > > > > > > > > diff --git a/drivers/media/i2c/alvium-csi2.c b/drivers/media/i2c/alvium-csi2.c
> > > > > > > > > new file mode 100644
> > > > > > > > > index 000000000000..52c9263075cf
> > > > > > > > > --- /dev/null
> > > > > > > > > +++ b/drivers/media/i2c/alvium-csi2.c
> > > > > > > > > @@ -0,0 +1,3479 @@
> > > > > 
> > > > > [snip]
> > > > > 
> > > > > > > > > +static int alvium_get_img_width_params(struct alvium_dev *alvium)
> > > > > > > > > +{
> > > > > > > > > +	struct device *dev = &alvium->i2c_client->dev;
> > > > > > > > > +	int ret;
> > > > > > > > > +	u64 val;
> > > > > > > > > +
> > > > > > > > > +	if (!alvium->bcrm_addr)
> > > > > > > > > +		return -EINVAL;
> > > > > > > > > +
> > > > > > > > > +	ret = alvium_read(alvium,
> > > > > > > > > +			  REG_BCRM_IMG_WIDTH_MIN_R,
> > > > > > > > > +			  &val);
> > > > > > > > > +	if (ret) {
> > > > > > > > > +		dev_err(dev, "Fail to read img min width reg\n");
> > > > > > > > > +		return ret;
> > > > > > > > > +	}
> > > > > > > > 
> > > > > > > > Could you add a macro that assigns the value to the variable (or a struct
> > > > > > > > field in this case) when the read is successful? Add the print if you think
> > > > > > > > you need it.
> > > > > > > 
> > > > > > > I don't get this comment.
> > > > > > > Can you explain me better your plan please.
> > > > > > 
> > > > > > You have exactly the same pattern repeated over and over in a number of
> > > > > > functions. I'd like you to add a macro (or a function) that takes what
> > > > > > varies as arguments, and call that function here. It would reduce a lot of
> > > > > > the repeated lines code here.
> > > > > > 
> > > > > > ...
> > > > > 
> > > > > The best option is to print an error message in alvium_read() and drop
> > > > > all error messages from the callers.
> > > > 
> > > > What about don't print anything? We already have prints that comes from
> > > > CCI API if some errors occurs. Laurent suggest me this into some
> > > > previous comments. Let me know.
> > > 
> > > We need to print something somewhere as silent failures are bad. The
> > > messages printed by the CCI helpers are good enough, so no need to print
> > > anything specific in the alvium driver.
> > 
> > Oooks I'll follow your way on v7, thanks Laurent.
> > My plan is to switch to the following implementation:
> > 
> > 
> > static int alvium_get_img_width_params(struct alvium_dev *alvium)
> > {
> > 	struct device *dev = &alvium->i2c_client->dev;
> > 	u64 val;
> > 	int ret = 0;
> > 
> > 	if (!alvium->bcrm_addr)
> > 		return -EINVAL;
> > 
> > 	alvium_read(alvium, REG_BCRM_IMG_WIDTH_MIN_R, &val, &ret);
> > 	alvium->img_min_width = val;
> > 	dev_dbg(dev, "Min img width: %d\n", alvium->img_min_width);
> > 
> > 	alvium_read(alvium, REG_BCRM_IMG_WIDTH_MAX_R, &val, NULL);
> 
> I assume you mean &ret and not NULL here.

Yes, sorry.
Wrong paste.

> 
> > 	alvium->img_max_width = val;
> > 	dev_dbg(dev, "Max img width: %d\n", alvium->img_max_width);
> > 
> > 	alvium_read(alvium, REG_BCRM_IMG_WIDTH_INC_R, &val, &ret);
> > 	alvium->img_inc_width = val;
> > 	dev_dbg(dev, "img width increment: %d px\n", alvium->img_inc_width);
> > 
> > 	return ret;
> > }
> > 
> > Like you suggest. :)
> > What do you think about?
> 
> I would probably drop the debug messages, or at least group them all in
> a single message at the end of the function to print all three values.
> You should also not print the values if an error occurs during the
> reads, as they will be undefined.
> 
> In general, while debug messages are useful, they should be used with
> parcimony. Printing every single parameter passed by userspace, or
> adding a debug message at the beginning of every function, would make
> the kernel log very noisy and doesn't bring that much value.

Ok, I'll try to collect your hints in v7.

Thanks,
Tommaso

> 
> -- 
> Regards,
> 
> Laurent Pinchart