The sequencer API is totally recoded with the style of "encapsulation"
in other api.
The structure becomes opaque and accessed only via functions.
Other changes:
- There is no longer group in client and port info.
- snd_seq_query_subs_t is renamed to snd_seq_query_subscribe_t.
- snd_seq_delete_port takes only the port id argument instead of
port_info structure.
- snd_seq_input/output_buffer_size are renamed
as snd_seq_get_input/output_buffer_size.
Similarly snd_seq_resize_input/output_buffer are renamed as
snd_seq_set_input/output_buffer_size.
- snd_seq_get_named_queue is renamed to snd_seq_query_named_queue.
- Sync codes are removed temporarily from API.
- Subscription conditions are accessed via the corresponding functions.
convert_time is named now as time_update.
- snd_seq_get/set_queue_owner are removed.
Use snd_seq_get/set_queue_info instead.
- Instrument put/get/remove structure is unified as snd_instr_header_t.
They are half-automated output from the 0.5.x documents.
The sequencer API will be changed in near future
to suit with encapsulation implemented already in pcm api,
so do not trust the comments added here..
They are just for reference.
- dead SMP lock in es1968 (maestro2) driver.
Bugfix & enhances of sequencer stuff
by Scott McNab <sdm@fractalgraphics.com.au>:
- fix for the insrument list locking in SND_SEQ_EVENT_INSTR_BEGIN
and SND_SEQ_EVENT_INSTR_END events.
Note that nothing seems to really take notice of the list locking.
This is more an issue when we add support for editing instruments
anyway.
- added new alsa-lib utility function snd_seq_ev_set_varusr() which
is similar to snd_seq_ev_set_variable(), but specifies userspace
extended event data.
This is required in order to use the SND_SEQ_EVENT_INSTR_PUT
command (took me bloody ages to work this out btw)
- minor correction for gus & trident synth drivers
Wed, 22 Dec 1999 15:51:37 +0100
Changes in alsa-driver:
1. SND_SEQ_DEST_DIRECT was removed. For direct dispatching, specify
the scheduling queue as SND_SEQ_QUEUE_DIRECT.
Source compatibility is kept if alsa-lib functions are used to set
or check direct mode.
Tested: pmidi, playmidi1, aconnect, aseqview, OSS emulation
2. The error event can be bounced to the sender as an encapsulated
event with SND_SEQ_EVENT_BOUNCE type. If the orignal event is
variable length (like SYSEX), the data body is added after the
copied event data. (To access to it, use
snd_seq_event_bounce_ext_data() macro.)
This feature is enabled only when the sender is opened with read
flag and has a client-filter flag SND_SEQ_FILTER_BOUNCE, so that
as default it is disabled.
3. Maximum size of VARIABLE length event is defined as 2048 bytes.
Larger events will be refused.
Note that this is not the size of VARUSR nor VARIPC event.
4. Return error code was revised.
Possible errors for read():
-ENXIO invalid client or file open mode
-ENOSPC FIFO overflow (the flag is cleared after this error report)
-EINVAL no enough user-space buffer to write the whole event
-EFAULT seg. fault during copy to user space
Possible errors for write():
-ENXIO invalid client or file open mode
-ENOMEM malloc failed
-EFAULT seg. fault during copy from user space
-EINVAL invalid event
-EAGAIN no space in output pool
-EINTR interrupts while sleep
-EMLINK too many hops
others depends on return value from driver event_input callback
Changes in alsa-lib:
5. Behavior of snd_seq_flush_output() was changed.
It flushes data in output buffer as much as possible. This has
two advantages. One is that most data can be sent at one call,
and another is that the error in write() can be detected directly
from this function.
The demerit of this implementation is that in non-blocking mode, it
tries twice write() even if write pool of sequencer is full, which
is not actually error. In this case, flush_output() always returns
-EAGAIN error code.
After an error is detected (except for -EAGAIN in non-blocking
mode), you should remove the error event via
snd_seq_extract_output() as below. Otherwise, it'll remain in
output buffer and cause the same error again.
6. Some functions were added:
snd_seq_exract_output(seq, &event)
This extracts the first event on *output* buffer. This will
be useful to know (and remove) the event which causes error in
write().
snd_seq_event_input_pending(seq, fetch)
Retunrs the number of events on input buffer.
If no events exist in input buffer, it fetches from sequencer
(only when flag is true).
snd_seq_event_input_selective(seq, &ev, type, blocking)
Retrieve the event from input with the given event type.
If blocking is true, it waits until the target event is
received. It'll be useful for checking bounced error or
waiting for hand-shake results (eg. loading insruments).
Fri, 17 Sep 1999 17:24:43 +0200
OK, the attached is the patch to alsa-driver and alsa-lib.
It will really violate the source/binary compatibility as
I wrote :-p
It includes:
- change of event data for accessing Timer Port
- new middle-level functions for sequencer in alsa-lib
- some comments / fixes
The test programs in alsa-lib (playmidi1, aconnect, aseqnet)
were rewritten to use the new functions above.
I included also a patch to pmidi-1.2.2.
