From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752994Ab1AYLSs (ORCPT ); Tue, 25 Jan 2011 06:18:48 -0500 Received: from mgw2.diku.dk ([130.225.96.92]:40373 "EHLO mgw2.diku.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752769Ab1AYLSr (ORCPT ); Tue, 25 Jan 2011 06:18:47 -0500 Date: Tue, 25 Jan 2011 12:18:40 +0100 (CET) From: Julia Lawall To: walter harms Cc: Russell King - ARM Linux , Vasiliy Kulikov , Ryan Mallon , kernel-janitors@vger.kernel.org, Nicolas Ferre , Jean-Christophe PLAGNIOL-VILLARD , Andrew Victor , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/4] arch/arm/mach-at91/clock.c: Add missing IS_ERR test In-Reply-To: <4D3EB02D.6090302@bfs.de> Message-ID: References: <1295898922-18822-1-git-send-email-julia@diku.dk> <1295898922-18822-3-git-send-email-julia@diku.dk> <4D3DD964.9020107@bluewatersys.com> <20110124200515.GA30963@albatros> <4D3EA6EC.5050305@bfs.de> <20110125104333.GE11507@n2100.arm.linux.org.uk> <4D3EB02D.6090302@bfs.de> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 25 Jan 2011, walter harms wrote: > > > Am 25.01.2011 11:43, schrieb Russell King - ARM Linux: > > On Tue, Jan 25, 2011 at 11:33:16AM +0100, walter harms wrote: > >> Would it be more easy to return NULL in the error case of clk_get() instead > >> of ERR_PTR(-ENOENT) ? > >> > >> So the default could be return NULL and an architecture depending solution > >> replacing that. > > > > That's not how the API is defined. The API defines error-pointers to be > > errors, everything should be considered valid. Please don't go down the > > route of doing something architecturally different from that. > > > > What if, say, you couldn't return the struct clk because maybe it could > > only be controlled by one user? Returning an EBUSY error pointer would > > indicate this condition. What if the module providing the struct clk > > hasn't finished initializing - that's another reason for EBUSY rather > > than ENOENT. > > > > Error codes are useful to describe why something failed. NULL pointers > > can't do that. > > > > On Mon, 24 Jan 2011, Vasiliy Kulikov wrote: > > > ... > > clk_get() is defined per-architecture, sometimes it is NULL only. > > > > So these is a bug ? They should return -ENOENT ? > > The interessting question is: what to do with an error ? > > Obviously some architecture can live with NULL, so it is not an critical > error. An the patch shows a code that is simply a return, not even the > user is informed that something did not work as expected. > > From that point of view i would like question if it is useful to have > a "detailed" error instead of just returning NULL. Somewhat unrelatedly, I often run into code where error handling code is needed, but not present, and the function returns void, so nothing is provided for propagating the error further. I generally consider these cases to be beyond my expertise to fix... julia From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julia Lawall Date: Tue, 25 Jan 2011 11:18:40 +0000 Subject: Re: [PATCH 2/4] arch/arm/mach-at91/clock.c: Add missing IS_ERR test Message-Id: List-Id: References: <1295898922-18822-1-git-send-email-julia@diku.dk> <1295898922-18822-3-git-send-email-julia@diku.dk> <4D3DD964.9020107@bluewatersys.com> <20110124200515.GA30963@albatros> <4D3EA6EC.5050305@bfs.de> <20110125104333.GE11507@n2100.arm.linux.org.uk> <4D3EB02D.6090302@bfs.de> In-Reply-To: <4D3EB02D.6090302@bfs.de> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-arm-kernel@lists.infradead.org On Tue, 25 Jan 2011, walter harms wrote: > > > Am 25.01.2011 11:43, schrieb Russell King - ARM Linux: > > On Tue, Jan 25, 2011 at 11:33:16AM +0100, walter harms wrote: > >> Would it be more easy to return NULL in the error case of clk_get() instead > >> of ERR_PTR(-ENOENT) ? > >> > >> So the default could be return NULL and an architecture depending solution > >> replacing that. > > > > That's not how the API is defined. The API defines error-pointers to be > > errors, everything should be considered valid. Please don't go down the > > route of doing something architecturally different from that. > > > > What if, say, you couldn't return the struct clk because maybe it could > > only be controlled by one user? Returning an EBUSY error pointer would > > indicate this condition. What if the module providing the struct clk > > hasn't finished initializing - that's another reason for EBUSY rather > > than ENOENT. > > > > Error codes are useful to describe why something failed. NULL pointers > > can't do that. > > > > On Mon, 24 Jan 2011, Vasiliy Kulikov wrote: > > > ... > > clk_get() is defined per-architecture, sometimes it is NULL only. > > > > So these is a bug ? They should return -ENOENT ? > > The interessting question is: what to do with an error ? > > Obviously some architecture can live with NULL, so it is not an critical > error. An the patch shows a code that is simply a return, not even the > user is informed that something did not work as expected. > > From that point of view i would like question if it is useful to have > a "detailed" error instead of just returning NULL. Somewhat unrelatedly, I often run into code where error handling code is needed, but not present, and the function returns void, so nothing is provided for propagating the error further. I generally consider these cases to be beyond my expertise to fix... julia From mboxrd@z Thu Jan 1 00:00:00 1970 From: julia@diku.dk (Julia Lawall) Date: Tue, 25 Jan 2011 12:18:40 +0100 (CET) Subject: [PATCH 2/4] arch/arm/mach-at91/clock.c: Add missing IS_ERR test In-Reply-To: <4D3EB02D.6090302@bfs.de> References: <1295898922-18822-1-git-send-email-julia@diku.dk> <1295898922-18822-3-git-send-email-julia@diku.dk> <4D3DD964.9020107@bluewatersys.com> <20110124200515.GA30963@albatros> <4D3EA6EC.5050305@bfs.de> <20110125104333.GE11507@n2100.arm.linux.org.uk> <4D3EB02D.6090302@bfs.de> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Tue, 25 Jan 2011, walter harms wrote: > > > Am 25.01.2011 11:43, schrieb Russell King - ARM Linux: > > On Tue, Jan 25, 2011 at 11:33:16AM +0100, walter harms wrote: > >> Would it be more easy to return NULL in the error case of clk_get() instead > >> of ERR_PTR(-ENOENT) ? > >> > >> So the default could be return NULL and an architecture depending solution > >> replacing that. > > > > That's not how the API is defined. The API defines error-pointers to be > > errors, everything should be considered valid. Please don't go down the > > route of doing something architecturally different from that. > > > > What if, say, you couldn't return the struct clk because maybe it could > > only be controlled by one user? Returning an EBUSY error pointer would > > indicate this condition. What if the module providing the struct clk > > hasn't finished initializing - that's another reason for EBUSY rather > > than ENOENT. > > > > Error codes are useful to describe why something failed. NULL pointers > > can't do that. > > > > On Mon, 24 Jan 2011, Vasiliy Kulikov wrote: > > > ... > > clk_get() is defined per-architecture, sometimes it is NULL only. > > > > So these is a bug ? They should return -ENOENT ? > > The interessting question is: what to do with an error ? > > Obviously some architecture can live with NULL, so it is not an critical > error. An the patch shows a code that is simply a return, not even the > user is informed that something did not work as expected. > > From that point of view i would like question if it is useful to have > a "detailed" error instead of just returning NULL. Somewhat unrelatedly, I often run into code where error handling code is needed, but not present, and the function returns void, so nothing is provided for propagating the error further. I generally consider these cases to be beyond my expertise to fix... julia