linux-kernel - Re: [PATCH] staging: media/davinci_vpfe: fix pinmux setup compilation

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Date:   Mon, 22 Jul 2019 14:10:18 +0530
From:   Sekhar Nori <nsekhar@...com>
To:     Arnd Bergmann <arnd@...db.de>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:     Lad Prabhakar <prabhakar.csengg@...il.com>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Mukesh Ojha <mojha@...eaurora.org>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Ioannis Valasakis <code@...ofe.uk>,
        Arushi Singhal <arushisinghal19971997@...il.com>,
        <linux-media@...r.kernel.org>, <devel@...verdev.osuosl.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] staging: media/davinci_vpfe: fix pinmux setup compilation

Hi Arnd,

On 22/07/19 1:42 PM, Arnd Bergmann wrote:
> The dm365_isif staging driver uses an odd method for configuring its
> pin muxing by calling directly into low-level davinci platform specific
> code, even when being compile-tested for other platforms.
> 
> As we want davinci to be part of a multi-platform kernel, this will
> cause a build failure when those headers are no longer exported even
> for davinci:
> 
> drivers/staging/media/davinci_vpfe/dm365_isif.c: In function 'vpfe_isif_init':
> drivers/staging/media/davinci_vpfe/dm365_isif.c:2031:2: error: implicit declaration of function 'davinci_cfg_reg'; did you mean 'omap_cfg_reg'? [-Werror=implicit-function-declaration]
>   davinci_cfg_reg(DM365_VIN_CAM_WEN);
>   ^~~~~~~~~~~~~~~
>   omap_cfg_reg
> drivers/staging/media/davinci_vpfe/dm365_isif.c:2031:18: error: 'DM365_VIN_CAM_WEN' undeclared (first use in this function); did you mean 'DM365_ISIF_MAX_CLDC'?
>   davinci_cfg_reg(DM365_VIN_CAM_WEN);
>                   ^~~~~~~~~~~~~~~~~
> 
> Digging further, it seems that the platform data structures defined
> in drivers/staging/media/davinci_vpfe/vpfe.h are an incompatible
> version of the same structures in include/media/davinci/vpfe_capture.h,
> which is the version that is used by the platform code, so the
> combination that exists in the mainline kernel cannot be used.
> 
> The platform code already has an abstraction for the pinmux,
> in the form of the dm365_isif_setup_pinmux() helper. If we want
> to ever get to use the staging driver again, this needs to be
> read from the platform data passed to this driver, or rewritten
> to use the pinmux framework.
> 
> For the moment, pretend we pass the helper function in the
> staging platform driver to get it to build cleanly. I could
> not figure out how the staging driver relates to the code
> in drivers/media/platform/davinci/, some clarification on that
> would be helpful to decide what the long-term plan on this
> should be to either remove the staging driver as obsolete or
> integrate it with the rest in a way that actually works.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

I looked at the history of updates on this driver over last 4 years.
None of them are towards fixing some issue found with the driver during
actual usage or for improving its design to move it out of staging.

I think no one is really using it or working on moving it out of
staging. Perhaps the right thing to do would be to delete it.

Thanks,
Sekhar