Re: MIDI+USB - one way?

[Takashi Iwai <tiwai@suse.de>]

At Mon, 05 Aug 2002 10:43:28 +0200,
Clemens Ladisch wrote:
> 
> Jaroslav Kysela wrote:
> > On Fri, 2 Aug 2002, Clemens Ladisch wrote:
> > > rawmidi.c uses the ALSA library functions to access the rawmidi device.
> > > Internally, alsa-lib should use the same read() call as cat, but there
> > > seems to be a difference somewhere, maybe in the initialization.
> > 
> > Note that the cat utility (od probably too) uses big input buffer. If you
> > want to capture byte-stream, use the dd utility with the block size of 1
> > byte.
> 
> No, the size of the input buffer must not prevent read() from returning
> data which is available immediately.  IOW: if some data is available,
> read() mustn't block.  ALSA's current read() implementation is wrong in
> this regard.
> 
> This isn't only incompatible to OSS, but also to any other implementation
> of read() in Linux (or any other Unix-like OS, not to mention POSIX or
> SUS).

how about pcm?  it must be blocked unless O_NONBLOCK is specified.

this issue is regardless how the other unix-like os are, but we need
to refer to _only_ posix here.  eventually, linux is not a unix clone
:)

imo, in the case of midi, this blocking behavior is nothting but
annoying.  hence i agree to change this behavior, as long as the
change doesn't break the posix standard.
(and i believe that no applications suffer by this change.)


Takashi


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