linux-kernel - Re: [PATCH] staging: vme: fix error return code in vme_user

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Date:	Tue, 14 May 2013 14:56:17 +0100
From:	Martyn Welch <martyn.welch@...com>
To:	Dan Carpenter <dan.carpenter@...cle.com>
CC:	Wei Yongjun <weiyj.lk@...il.com>, gmate.amit@...il.com,
	devel@...verdev.osuosl.org, manohar.vanga@...il.com,
	gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
	yamanetoshi@...il.com, yongjun_wei@...ndmicro.com.cn,
	joe@...ches.com
Subject: Re: [PATCH] staging: vme: fix error return code in vme_user_probe()

On 13/05/13 09:51, Dan Carpenter wrote:
> On Mon, May 13, 2013 at 09:16:00AM +0100, Martyn Welch wrote:
>> On 13/05/13 07:05, Wei Yongjun wrote:
>>> From: Wei Yongjun <yongjun_wei@...ndmicro.com.cn>
>>>
>>> Fix to return -ENOMEM in the resource alloc error handling
>>> case instead of 0, as done elsewhere in this function.
>>>
>>
>> Hi Wei,
>>
>> Thanks for your patch. As this is resource allocation rather than memory
>> allocation that is failing, would -EAGAIN not make more sense than -ENOMEM?
>>
> 
> ENOMEM is better.  EAGAIN is for when trylock() fails etc.  In other
> words we are not allowed to block and someone is using the lock we
> need.
> 

ENOMEM just doesn't seem to describe the error very well. This error will be
triggered if no free VME windows are available for the driver to use - there
are typically 8 master and 8 slave windows provided in hardware.

How about EBUSY (Device or resource busy)?

> It feels like we discuss error codes a lot on LKML and they should
> be documented under Documententation/.  The closest thing is
> Documentation/i2c/fault-codes.
> 

I'd been looking at the errno man page since I was under the impression that
these values would typically find their way back to user space.

Martyn

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