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Date:   Thu, 29 Jul 2021 19:50:43 +0530
From:   Ojaswin Mujoo <ojaswin98@gmail.com>
To:     Stefan Wahren <stefan.wahren@i2se.com>
Cc:     Greg KH <gregkh@linuxfoundation.org>, nsaenz@kernel.org,
        dan.carpenter@oracle.com, phil@raspberrypi.com,
        linux-arm-kernel@lists.infradead.org,
        linux-staging@lists.linux.dev, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] staging: vchiq: Set $CONFIG_VCHIQ_CDEV to be enabled
 by default
Message-ID: <20210729142043.GA25192@ojas>
References: <cover.1627495116.git.ojaswin98@gmail.com>
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 <20210728200607.GB17046@ojas>
 <ddcc0ba2-edc0-89a9-b20d-ce58b3e548fc@i2se.com>
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On Wed, Jul 28, 2021 at 10:21:41PM +0200, Stefan Wahren wrote:
> Am 28.07.21 um 22:06 schrieb Ojaswin Mujoo:
> > On Wed, Jul 28, 2021 at 08:45:55PM +0200, Greg KH wrote:
> >> On Thu, Jul 29, 2021 at 12:07:16AM +0530, Ojaswin Mujoo wrote:
> >>> Before this config was defined, the cdev used to be created
> >>> unconditionally. When an earlier commit introduced this config, the
> >>> default behavior was set to disabled, which might surprise some
> >>> unsuspecting users.  Hence, make this config default to 'Y' to be more
> >>> backward consistent.
> >>>
> >>> Signed-off-by: Ojaswin Mujoo <ojaswin98@gmail.com>
> >>> ---
> >>>  drivers/staging/vc04_services/Kconfig | 1 +
> >>>  1 file changed, 1 insertion(+)
> >>>
> >>> diff --git a/drivers/staging/vc04_services/Kconfig b/drivers/staging/vc04_services/Kconfig
> >>> index 63caa6818d37..2b70c37cdd09 100644
> >>> --- a/drivers/staging/vc04_services/Kconfig
> >>> +++ b/drivers/staging/vc04_services/Kconfig
> >>> @@ -23,6 +23,7 @@ if BCM2835_VCHIQ
> >>>  
> >>>  config VCHIQ_CDEV
> >>>  	bool "VCHIQ Character Driver"
> >>> +	default y
> >>
> >> default y is only if the machine will not work without this option.
> >> Is that the case here?  If not, then please do not have this as the
> >> default.
> > Got it Greg. 
> >
> > From my testing, the Raspberry Pi does seem to boot correctly without
> > this although some userspace libraries might not work. 
> >
> > Since the machine itself works, I guess I'll drop this patch.
> 
> The idea is good, but the patch needs improvement :)
> 
> Acceptable solution might be that BCM2835_VCHIQ selects VCHIQ_CDEV.
Thanks for the suggestion, Stefan. 

So on testing with select, it seems like select defines a hard reverse
dependency i.e if BCM2835_VCHIQ=y then VCHIQ_CDEV=y and it can't be set
to n.

Checking the Kconfig launguae doc, I found that we could use "imply" to
define weak reverse dependencies, such that BCM2835_VCHIQ=y auto selects
VCHIQ_CDEV=y but we can also change it back to n if required. I tested
this out and it seems to work fine. I believe we can se imply here as it
better suits the use case.

Thank you,
Ojaswin
> 
> >
> > Thank you!
> > Ojaswin
> >> thanks,
> >>
> >> greg k-h
> > _______________________________________________
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> > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>