linux-kernel - Re: [V2] mtd: devices: docg3:- Handle return value of devm

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Date:   Mon, 12 Dec 2016 23:45:55 +0530
From:   arvind Yadav <arvind.yadav.cs@...il.com>
To:     Boris Brezillon <boris.brezillon@...e-electrons.com>
Cc:     robert.jarzmik@...e.fr, dwmw2@...radead.org,
        computersforpeace@...il.com, marek.vasut@...il.com, richard@....at,
        cyrille.pitchen@...el.com, linux-mtd@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [V2] mtd: devices: docg3:- Handle return value of devm_ioremap.

Hi Boris,

Yes, It's possible that two driver can use same iomem region.
For example you can check
commit id - : 33cf75656923ff11d67a937a4f8e9344f58cea77

Here, It's not required.

Thanks
-Arvind

On Monday 12 December 2016 10:34 PM, Boris Brezillon wrote:
> Hi Arvind,
>
> On Mon, 12 Dec 2016 21:33:05 +0530
> arvind Yadav <arvind.yadav.cs@...il.com> wrote:
>
>> There is problem, if you will use devm_ioremap_resource instead of
>> devm_ioremap,
>> than devm_ioremap_resource will call request_mem_region().
>> request_mem_region() allows to tell the kernel that this driver is going
>> to use
>> this range of I/O addresses, which will prevent other drivers to make an
>> overlapping call to request_mem_region If other driver want to use same
>> address
>> space to access then it will not allow. Means we can not share same
>> address space
>> between two driver.
> The question is, is it required here? In general, allowing 2 different
> drivers from touching the same iomem region is a bad idea, so, if
> there's a reason to allow that here, I'd like to know more about it.
>
> Thanks,
>
> Boris