linux-kernel - Re: [PATCH 2/2] staging: vchiq: Add details to $CONFIG_VCHIQ_CDEV help text

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Message-ID: <20210729134739.GA19228@ojas>
Date:   Thu, 29 Jul 2021 19:17:52 +0530
From:   Ojaswin Mujoo <ojaswin98@...il.com>
To:     Stefan Wahren <stefan.wahren@...e.com>
Cc:     Greg KH <gregkh@...uxfoundation.org>, nsaenz@...nel.org,
        dan.carpenter@...cle.com, phil@...pberrypi.com,
        linux-arm-kernel@...ts.infradead.org,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] staging: vchiq: Add details to $CONFIG_VCHIQ_CDEV
 help text

On Wed, Jul 28, 2021 at 10:39:38PM +0200, Stefan Wahren wrote:
> Am 28.07.21 um 22:00 schrieb Ojaswin Mujoo:
> > On Wed, Jul 28, 2021 at 08:46:51PM +0200, Greg KH wrote:
> >> On Thu, Jul 29, 2021 at 12:07:17AM +0530, Ojaswin Mujoo wrote:
> >>> Add some details to the Kconfig definition of $CONFIG_VCHIQ_CDEV to help
> >>> make the motive behind it a bit more clear.
> >>>
> >>> Signed-off-by: Ojaswin Mujoo <ojaswin98@...il.com>
> >>> ---
> >>>  drivers/staging/vc04_services/Kconfig | 8 ++++++--
> >>>  1 file changed, 6 insertions(+), 2 deletions(-)
> >>>
> >>> diff --git a/drivers/staging/vc04_services/Kconfig b/drivers/staging/vc04_services/Kconfig
> >>> index 2b70c37cdd09..cb02d8a4cb74 100644
> >>> --- a/drivers/staging/vc04_services/Kconfig
> >>> +++ b/drivers/staging/vc04_services/Kconfig
> >>> @@ -25,8 +25,12 @@ config VCHIQ_CDEV
> >>>  	bool "VCHIQ Character Driver"
> >>>  	default y
> >>>  	help
> >>> -		Enable the creation of VCHIQ character driver to help
> >>> -		communicate with the Videocore platform.
> >>> +		Enable the creation of VCHIQ character driver to help communicate
> >>> +		with the VideoCore platform. The cdev exposes ioctls used by
> >>> +		userspace libraries and testing tools to interact with VideoCore.
> >>> +		This can be set to 'N' if the VideoCore communication is not needed
> >>> +		by userspace but only by other kernel modules (like bcm2835-audio).
> >>> +		If not sure, set this to 'Y'.
> >> I still do not understand if I need this driver or not, and I have this
> >> hardware!  What functionality does this driver accomplish?  What is
> >> VideoCore?
> > Hey Greg,
> >
> > I believe I can add this under the CONFIG_BCM2835_VCHIQ config option,
> > as that enables the core driver that implements the functions to
> > communicate with VideoCore platform? 
> 
> Sorry, today i'm too tired to give a good explanation. VideoCore is the
> VPU inside the BCM283x SoC. It runs a firmware and VCHIQ provides a way
> to communicate with this firmware / VPU. The VCHIQ driver is required to
> get access to the audio jack and camera interface (see depending drivers).
> 
> Unfortunately i don't have an application list by the hand which uses
> the CDEV interface for VCHIQ, please use this link [1] as a starting point.
> 
> [1] - https://github.com/raspberrypi/userland
> 
Hi Stefan

Thanks for the brief, its good enough to help me get started. I've also
been looking more closely into this driver in my free time lately and I
can try to come up with a small summary to use as the help text. I'll
add it in v2 of this patch.

Regards,
Ojaswin
> >
> > This config option merely adds a cdev which exposes the the core
> > driver's functionality to userspace. 
> >
> > Regards,
> > Ojaswin
> >> thanks,
> >>
> >> greg k-h
> > _______________________________________________
> > linux-arm-kernel mailing list
> > linux-arm-kernel@...ts.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> 

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