From: Jaroslav Kysela <perex@perex.cz>
To: alsa-devel@alsa-project.org
Subject: Re: alsa-lib's new API issue (snd_ctl_elem_id_compare)
Date: Mon, 8 Mar 2021 15:33:46 +0100 [thread overview]
Message-ID: <5e26625d-3db1-0600-47f8-057c0101d6b1@perex.cz> (raw)
In-Reply-To: <20210308125817.GA212288@workstation>
Dne 08. 03. 21 v 13:58 Takashi Sakamoto napsal(a):
> Hi Jaroslav,
>
> I have some concern about your commit 2cfe6addaef6[1] for alsa-lib,
>
> It adds new library API, 'snd_ctl_elem_id_compare()', to compare a pair of
> IDs for control element. In the implementation, the API call returns 0 if
> they are the same, else negative or positive numeric value according to
> contents of the IDs.
I just noted that I didn't fill the function doc text correctly.
>
> My concerns are:
>
> 1. evaluation of numid field is not covered.
>
> This is not preferable since ALSA control core implementation covers two
> types of comparison; numid only, and the combination iface, device,
> subdevice, name, and index fields. If the API is produced for general use
> cases, it should correctly handle the numid-only case, in my opinion.
My motivation was to allow to use this function for qsort() for example. The
numid and full-field comparisons are two very different things.
> 2. tri-state return value is semantically inconsistent
It's correct for the sorting (strcmp like).
> The ID structure includes three types of values; integer, enumeration, and
> string. In my opinion, tri-state return value from them has different meaning
> each other.
True, the signess is the key, the value should be ignored.
> The reason I post this message instead of posting any fix is that the fix
> to the API affects to alsa-utils, in which the API is used by a patch you
> applied a few days ago[2]. The patch also includes change to 'AM_PATH_ALSA'
> declaration in configure.ac with bumped-up version to '1.2.5', and it
> disables to rebuild alsa-utils on the latest toolchain. (alsa-lib 1.2.5 is
> not released yet.)
The latest alsa-lib in the git repo is already set to 1.2.5pre1, so if you
upgrade alsa-lib, everything should be fine. I was a bit lazy to write a
configure test and add a wrapper to alsactl to support the older alsa-lib.
Jaroslav
--
Jaroslav Kysela <perex@perex.cz>
Linux Sound Maintainer; ALSA Project; Red Hat, Inc.
next prev parent reply other threads:[~2021-03-08 14:34 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-08 12:58 alsa-lib's new API issue (snd_ctl_elem_id_compare) Takashi Sakamoto
2021-03-08 14:33 ` Jaroslav Kysela [this message]
2021-03-09 0:38 ` Takashi Sakamoto
2021-03-09 12:37 ` Jaroslav Kysela
2021-03-11 12:46 ` Takashi Sakamoto
2021-03-11 13:22 ` Jaroslav Kysela
2021-03-12 1:35 ` Takashi Sakamoto
2021-03-12 10:09 ` Jaroslav Kysela
2021-03-14 1:41 ` Takashi Sakamoto
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