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d=suse.de; s=susede2_ed25519; t=1682067324; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=AxHo0Iox1y9iVl+JI051aDTxTiCiJfNB8sk6FuPa5mQ=; b=z3jQBOxj1cafUQEp/p0fzPk3vb8H6f5EX+tTp51GcBfxGluNM/3N4X8oJQCeuO4UyZJesT 7KbBNQpt6PrBpqBg== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 3D25013456; Fri, 21 Apr 2023 08:55:24 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id XPj4DXxPQmS7PQAAMHmgww (envelope-from ); Fri, 21 Apr 2023 08:55:24 +0000 Date: Fri, 21 Apr 2023 10:55:23 +0200 Message-ID: <87leilsjgk.wl-tiwai@suse.de> From: Takashi Iwai To: Oswald Buddenhagen Subject: Re: [RFC PATCH] docs: sound: kernel-api: writing-an-alsa-driver.rst: add FIXMEs In-Reply-To: References: <20230405201220.2197878-1-oswald.buddenhagen@gmx.de> <87sfddv7e4.wl-tiwai@suse.de> <87wn26u32c.wl-tiwai@suse.de> <87leimtyqw.wl-tiwai@suse.de> User-Agent: Wanderlust/2.15.9 (Almost Unreal) Emacs/27.2 Mule/6.0 MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII Message-ID-Hash: DPEB6TRL5Y76UYHTQLCLEYALMCQRJGED X-Message-ID-Hash: DPEB6TRL5Y76UYHTQLCLEYALMCQRJGED X-MailFrom: tiwai@suse.de X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; header-match-alsa-devel.alsa-project.org-0; header-match-alsa-devel.alsa-project.org-1; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: alsa-devel@alsa-project.org X-Mailman-Version: 3.3.8 Precedence: list List-Id: "Alsa-devel mailing list for ALSA developers - http://www.alsa-project.org" Archived-At: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On Thu, 20 Apr 2023 18:18:46 +0200, Oswald Buddenhagen wrote: > > On Thu, Apr 20, 2023 at 04:27:35PM +0200, Takashi Iwai wrote: > > But why this has to be buried in the middle of a patch containing lots > > of other changes...? Better to split out and start a new thread. > > > this "patch" doesn't contain any changes, only a bunch of questions. > given the expected audience, i don't think that "burying" it was > detrimental. Well, a patch is basically for patching -- i.e. fixing / correcting the stuff. For the basic API design topic, you could start off a thread, not as a form of a patch. > > IIRC, this was a result after struggles with the structured control > > implementations. It became too complex, and the plain array with > > string representation can cover all complexity, while it still allows > > the grouping in user-space side. > > > i can see how a keyword based interface description is appealing - it > keeps the kernel interface slim and flexible. but of course that comes > at a steep cost in user space - i for one got completely lost and was > unable to debug the bug described in the OP. > maybe a middle way would have been the best option? I don't mean that the current API is the best form, either. OTOH, it's been used for very long time, and the history tells that it's "good enough". > > Again, the choice was done in a quarter century ago, and if you change > > it, you'll certainly break the whole things badly. We must keep the > > compatibility. > > > i don't intend to actually change it. but suppose we did. > > i suppose we'd have to add SNDRV_CTL_ELEM_ACCESS_{PLAYBACK,CAPTURE}. > both could be set for unspecific and actually bidirectional > controls. if neither is set, user space would fall back to the keyword > based rules (and exceptions ...) - that would be backwards compatible > and would enable a gradual migration. The backward compatibility isn't really easy as you wrote, I'm afraid. If you run an old user-space stuff on the new kernel, you must not fill that new information bit but translate it to the string suffix instead; and that has to be done inside the kernel automagically. Takashi