diff options
Diffstat (limited to 'sound/firewire/fireface/ff-protocol-former.c')
| -rw-r--r-- | sound/firewire/fireface/ff-protocol-former.c | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/sound/firewire/fireface/ff-protocol-former.c b/sound/firewire/fireface/ff-protocol-former.c index e0acf40a02ee..8d1c2c6e907b 100644 --- a/sound/firewire/fireface/ff-protocol-former.c +++ b/sound/firewire/fireface/ff-protocol-former.c @@ -396,6 +396,10 @@ static void ff800_finish_session(struct snd_ff *ff) FF800_ISOC_COMM_STOP, ®, sizeof(reg), 0); } +// Fireface 800 doesn't allow drivers to register lower 4 bytes of destination +// address. +// A write transaction to clear registered higher 4 bytes of destination address +// has an effect to suppress asynchronous transaction from device. static void ff800_handle_midi_msg(struct snd_ff *ff, unsigned int offset, __le32 *buf, size_t length) { @@ -525,6 +529,25 @@ static void ff400_finish_session(struct snd_ff *ff) FF400_ISOC_COMM_STOP, ®, sizeof(reg), 0); } +// For Fireface 400, lower 4 bytes of destination address is configured by bit +// flag in quadlet register (little endian) at 0x'0000'801'0051c. Drivers can +// select one of 4 options: +// +// bit flags: offset of destination address +// - 0x04000000: 0x'....'....'0000'0000 +// - 0x08000000: 0x'....'....'0000'0080 +// - 0x10000000: 0x'....'....'0000'0100 +// - 0x20000000: 0x'....'....'0000'0180 +// +// Drivers can suppress the device to transfer asynchronous transactions by +// using below 2 bits. +// - 0x01000000: suppress transmission +// - 0x02000000: suppress transmission +// +// Actually, the register is write-only and includes the other options such as +// input attenuation. This driver allocates destination address with '0000'0000 +// in its lower offset and expects userspace application to configure the +// register for it. static void ff400_handle_midi_msg(struct snd_ff *ff, unsigned int offset, __le32 *buf, size_t length) { |