| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <20200725084740.GD829@valkosipuli.retiisi.org.uk>
Date: Sat, 25 Jul 2020 11:47:40 +0300
From: Sakari Ailus <sakari.ailus@....fi>
To: Kieran Bingham <kieran.bingham@...asonboard.com>
Cc: Kieran Bingham <kieran.bingham+renesas@...asonboard.com>,
linux-renesas-soc@...r.kernel.org, linux-media@...r.kernel.org,
linux-gpio@...r.kernel.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org,
Mauro Carvalho Chehab <mchehab@...nel.org>,
Laurent Pinchart <laurent.pinchart@...asonboard.com>,
Jacopo Mondi <jacopo@...ndi.org>,
Niklas Söderlund
<niklas.soderlund@...natech.se>, Hans Verkuil <hverkuil@...all.nl>,
Hyun Kwon <hyunk@...inx.com>,
Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
Rob Herring <robh+dt@...nel.org>,
Linus Walleij <linus.walleij@...aro.org>,
Jacopo Mondi <jacopo+renesas@...ndi.org>,
Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>,
Niklas Söderlund
<niklas.soderlund+renesas@...natech.se>
Subject: Re: [PATCH v10 2/4] media: i2c: Add MAX9286 driver
Kieran,
On Fri, Jul 24, 2020 at 10:32:11AM +0100, Kieran Bingham wrote:
> Hi Sakari,
>
> On 23/07/2020 23:28, Sakari Ailus wrote:
> > Hi Kieran,
> >
> > On Thu, Jul 16, 2020 at 10:02:24AM +0100, Kieran Bingham wrote:
> >> Hi Sakari,
> >>
> >> This is the output of checkpatch --strict on this driver. Sorry for not
> >> detailing this in the commit or cover letter.
> >
> > No worries.
> >
> >>
> >>> ./patches/gmsl/v10/v10-0001-dt-bindings-media-i2c-Add-bindings-for-Maxim-Int.patch has style problems, please review.
> >>> --------------------------------------------------------------
> >>> ./patches/gmsl/v10/v10-0002-media-i2c-Add-MAX9286-driver.patch
> >>> --------------------------------------------------------------
> >>> CHECK: Prefer using the BIT macro
> >>> #246: FILE: drivers/media/i2c/max9286.c:40:
> >>> +#define MAX9286_FSYNCMODE_INT_OUT (1 << 6)
> >>>
> >>> CHECK: Prefer using the BIT macro
> >>> #251: FILE: drivers/media/i2c/max9286.c:45:
> >>> +#define MAX9286_FSYNCMETH_SEMI_AUTO (1 << 0)
> >>>
> >>> CHECK: Prefer using the BIT macro
> >>> #262: FILE: drivers/media/i2c/max9286.c:56:
> >>> +#define MAX9286_EDC_6BIT_CRC (1 << 5)
> >>>
> >>> CHECK: Prefer using the BIT macro
> >>> #268: FILE: drivers/media/i2c/max9286.c:62:
> >>> +#define MAX9286_HVSRC_D14 (1 << 0)
> >>>
> >>> CHECK: Prefer using the BIT macro
> >>> #286: FILE: drivers/media/i2c/max9286.c:80:
> >>> +#define MAX9286_DATATYPE_RGB565 (1 << 0)
> >>>
> >>> CHECK: Prefer using the BIT macro
> >>> #304: FILE: drivers/media/i2c/max9286.c:98:
> >>> +#define MAX9286_I2CSLVSH_469NS_234NS (1 << 5)
> >>>
> >>> CHECK: Prefer using the BIT macro
> >>> #312: FILE: drivers/media/i2c/max9286.c:106:
> >>> +#define MAX9286_I2CMSTBT_28KBPS (1 << 2)
> >>>
> >>> CHECK: Prefer using the BIT macro
> >>> #316: FILE: drivers/media/i2c/max9286.c:110:
> >>> +#define MAX9286_I2CSLVTO_256US (1 << 0)
> >>
> >> None of those are appropriate to use the BIT() macro, as they are all
> >> entries of a specific field with a shift, such as:
> >>
> >> #define MAX9286_FSYNCMODE_ECU (3 << 6)
> >> #define MAX9286_FSYNCMODE_EXT (2 << 6)
> >> #define MAX9286_FSYNCMODE_INT_OUT (1 << 6)
> >> #define MAX9286_FSYNCMODE_INT_HIZ (0 << 6)
> >>
> >> Checkpatch is only picking up on the "1 << x" variant of each entry.
> >
> > Ideally you should use "1U << x" everywhere. If you happen to have a
> > register with 31st bit signifying something, mayhem would follow. So the
> > practice is to make all such definitions unsigned.
>
> Just to clarify, because of the location you've put your x, which is not
> the variable in the above case.
>
> These definitions are possible field values with a shift (enum << y),
> not bit values (1 << x)
>
> They can of course be unsigned though.
>
> Is your statement that you would like to see these as:
>
> #define MAX9286_FSYNCMODE_ECU (3U << 6)
> #define MAX9286_FSYNCMODE_EXT (2U << 6)
> #define MAX9286_FSYNCMODE_INT_OUT (1U << 6)
> #define MAX9286_FSYNCMODE_INT_HIZ (0U << 6)
Yes, please. This avoids shifting a non-zero bit to the 31st position of a
32-bit register.
>
>
> Or that you would prefer a macro'ised version:
>
> #define FIELD_ENTRY(value, shift) (value U << shift)
>
>
> Or rather, I could just convert them all to use FIELD_PREP:
>
> #define MAX9286_FSYNCMODE GENMASK(7,6)
>
> #define MAX9286_FSYNCMODE_ECU FIELD_PREP(MAX9286_FSYNCMODE, 3)
> #define MAX9286_FSYNCMODE_EXT FIELD_PREP(MAX9286_FSYNCMODE, 2)
> #define MAX9286_FSYNCMODE_INT_OUT FIELD_PREP(MAX9286_FSYNCMODE, 1)
> #define MAX9286_FSYNCMODE_INT_HIZ FIELD_PREP(MAX9286_FSYNCMODE, 0)
>
> If you want me to change these entries, I suspect moving wholly to use
> FIELD_PREP/FIELD_GET throughout the driver would be the best course of
> action.
>
> A bit of churn, but I can do that if you wish.
>
> --
> Kieran
>
>
>
> >>> CHECK: Macro argument reuse 'source' - possible side-effects?
> >>> #399: FILE: drivers/media/i2c/max9286.c:193:
> >>> +#define for_each_source(priv, source) \
> >>> + for ((source) = NULL; ((source) = next_source((priv), (source))); )
> >>
> >> This warns against possible side effects, but the 're-use' effects are
> >> desired ;-)
> >>
> >> If you'd prefer this macro to be re-written please let me know.
> >
> > Works for me. Some warnigns are just not useful. I bet quite a few macros
> > elsewhere in the kernel would trigger this.
>
>
> I think we'll just leave this one ;-)
>
>
> >>> CHECK: Lines should not end with a '('
> >>> #1372: FILE: drivers/media/i2c/max9286.c:1166:
> >>> + ret = v4l2_fwnode_endpoint_parse(
> >>
> >> Full code block:
> >>
> >>> ret = v4l2_fwnode_endpoint_parse(
> >>> of_fwnode_handle(node), &vep);
> >>> if (ret) {
> >>> of_node_put(node);
> >>> return ret;
> >>> }
> >>
> >> That one is awkward, and I chose to keep it as a lesser evil.
> >> Of course now that we can officially go up to 120 chars, I could move
> >> this line up.
> >>
> >> If you'd like this to be moved to a single line now we can go over 80
> >> chars, please confirm.
> >
> > I don't mind that. Mauro, any thoughts on this?
>
>
> And I'll let Mauro decide that as it will impact my line-length choices
> in the future ;-)
I think it's actually much better to end a line with opening parenthesis
than have a line longer than 80, but I recognise there are differing
opinions.
My terminal window width is 80 and having more terminals is more useful
than being able to see a rare line over 80 completely.
--
Regards,
Sakari Ailus
Powered by blists - more mailing lists