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ALSA: mpu401: clean up interrupt specification

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The semantics of snd_mpu401_uart_new()'s interrupt parameters are
somewhat counterintuitive:  To prevent the function from allocating its
own interrupt, either the irq number must be invalid, or the irq_flags
parameter must be zero.  At the same time, the irq parameter being
invalid specifies that the mpu401 code has to work without an interrupt
allocated by the caller.  This implies that, if there is an interrupt
and it is allocated by the caller, the irq parameter must be set to
a valid-looking number which then isn't actually used.

With the removal of IRQF_DISABLED, zero becomes a valid irq_flags value,
which forces us to handle the parameters differently.

This patch introduces a new flag MPU401_INFO_IRQ_HOOK for when the
device interrupt is handled by the caller, and makes the allocation of
the interrupt to depend only on the irq parameter.  As suggested by
Takashi, the irq_flags parameter was dropped because, when used, it had
the constant value IRQF_DISABLED.

Signed-off-by: Clemens Ladisch <[email protected]>
Signed-off-by: Takashi Iwai <[email protected]>
This commit is contained in:
Clemens Ladisch 2011-09-13 11:24:41 +02:00 • committed by Takashi Iwai
commit dba8b46992
38 changed files with 103 additions and 94 deletions
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36
Documentation/DocBook/writing-an-alsa-driver.tmpl
View file

@ -4288,7 +4288,7 @@ struct _snd_pcm_runtime {
<![CDATA[
struct snd_rawmidi *rmidi;
snd_mpu401_uart_new(card, 0, MPU401_HW_MPU401, port, info_flags,
irq, irq_flags, &rmidi);
irq, &rmidi);
]]>
</programlisting>
</informalexample>
@ -4343,6 +4343,13 @@ struct _snd_pcm_runtime {
by itself to start processing the output stream in the irq handler.
</para>
<para>
If the MPU-401 interface shares its interrupt with the other logical
devices on the card, set <constant>MPU401_INFO_IRQ_HOOK</constant>
(see <link linkend="midi-interface-interrupt-handler"><citetitle>
below</citetitle></link>).
</para>
<para>
Usually, the port address corresponds to the command port and
port + 1 corresponds to the data port. If not, you may change
@ -4375,14 +4382,12 @@ struct _snd_pcm_runtime {
</para>
<para>
The 6th argument specifies the irq number for UART. If the irq
is already allocated, pass 0 to the 7th argument
(<parameter>irq_flags</parameter>). Otherwise, pass the flags
for irq allocation
(<constant>SA_XXX</constant> bits) to it, and the irq will be
reserved by the mpu401-uart layer. If the card doesn't generate
UART interrupts, pass -1 as the irq number. Then a timer
interrupt will be invoked for polling.
The 6th argument specifies the ISA irq number that will be
allocated. If no interrupt is to be allocated (because your
code is already allocating a shared interrupt, or because the
device does not use interrupts), pass -1 instead.
For a MPU-401 device without an interrupt, a polling timer
will be used instead.
</para>
</section>
@ -4390,12 +4395,13 @@ struct _snd_pcm_runtime {
<title>Interrupt Handler</title>
<para>
When the interrupt is allocated in
<function>snd_mpu401_uart_new()</function>, the private
interrupt handler is used, hence you don't have anything else to do
than creating the mpu401 stuff. Otherwise, you have to call
<function>snd_mpu401_uart_interrupt()</function> explicitly when
a UART interrupt is invoked and checked in your own interrupt
handler.
<function>snd_mpu401_uart_new()</function>, an exclusive ISA
interrupt handler is automatically used, hence you don't have
anything else to do than creating the mpu401 stuff. Otherwise, you
have to set <constant>MPU401_INFO_IRQ_HOOK</constant>, and call
<function>snd_mpu401_uart_interrupt()</function> explicitly from your
own interrupt handler when it has determined that a UART interrupt
has occurred.
</para>
<para>