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

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Date:   Mon, 12 Dec 2016 18:04:44 +0100
From:   Boris Brezillon <boris.brezillon@...e-electrons.com>
To:     arvind Yadav <arvind.yadav.cs@...il.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 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