From mboxrd@z Thu Jan 1 00:00:00 1970 From: walter harms Date: Tue, 25 Jan 2011 11:12:45 +0000 Subject: Re: [PATCH 2/4] arch/arm/mach-at91/clock.c: Add missing IS_ERR test Message-Id: <4D3EB02D.6090302@bfs.de> 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> In-Reply-To: <20110125104333.GE11507@n2100.arm.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-arm-kernel@lists.infradead.org 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. just my 2 cents, re, wh