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-rw-r--r--sound/firewire/fireface/ff-protocol-former.c23
-rw-r--r--sound/firewire/fireface/ff-protocol-latter.c18
-rw-r--r--sound/firewire/fireface/ff-transaction.c36
3 files changed, 48 insertions, 29 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, &reg, 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, &reg, 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)
{
diff --git a/sound/firewire/fireface/ff-protocol-latter.c b/sound/firewire/fireface/ff-protocol-latter.c
index 817af4447349..0fbc1950327f 100644
--- a/sound/firewire/fireface/ff-protocol-latter.c
+++ b/sound/firewire/fireface/ff-protocol-latter.c
@@ -266,6 +266,24 @@ static void latter_dump_status(struct snd_ff *ff, struct snd_info_buffer *buffer
// NOTE: transactions are transferred within 0x00-0x7f in allocated range of
// address. This seems to be for check of discontinuity in receiver side.
+//
+// Like Fireface 400, drivers can select one of 4 options for lower 4 bytes of
+// destination address by bit flags in quadlet register (little endian) at
+// 0x'ffff'0000'0014:
+//
+// bit flags: offset of destination address
+// - 0x00002000: 0x'....'....'0000'0000
+// - 0x00004000: 0x'....'....'0000'0080
+// - 0x00008000: 0x'....'....'0000'0100
+// - 0x00010000: 0x'....'....'0000'0180
+//
+// Drivers can suppress the device to transfer asynchronous transactions by
+// clear these bit flags.
+//
+// Actually, the register is write-only and includes the other settings such as
+// input attenuation. This driver allocates for the first option
+// (0x'....'....'0000'0000) and expects userspace application to configure the
+// register for it.
static void latter_handle_midi_msg(struct snd_ff *ff, unsigned int offset,
__le32 *buf, size_t length)
{
diff --git a/sound/firewire/fireface/ff-transaction.c b/sound/firewire/fireface/ff-transaction.c
index d8a8b01b39a1..0d6ad19363b8 100644
--- a/sound/firewire/fireface/ff-transaction.c
+++ b/sound/firewire/fireface/ff-transaction.c
@@ -165,35 +165,13 @@ static int allocate_own_address(struct snd_ff *ff, int i)
return err;
}
-/*
- * Controllers are allowed to register higher 4 bytes of address to receive
- * the transactions. Different models have different registers for this purpose;
- * e.g. 0x'0000'8010'03f4 for Fireface 400.
- * The controllers are not allowed to register lower 4 bytes of the address.
- * They are forced to select one of 4 options for the part of address by writing
- * corresponding bits to 0x'0000'8010'051f.
- *
- * The 3rd-6th bits of this register are flags to indicate lower 4 bytes of
- * address to which the device transferrs the transactions. In short:
- * - 0x20: 0x'....'....'0000'0180
- * - 0x10: 0x'....'....'0000'0100
- * - 0x08: 0x'....'....'0000'0080
- * - 0x04: 0x'....'....'0000'0000
- *
- * This driver configure 0x'....'....'0000'0000 to receive MIDI messages from
- * units. The 3rd bit of the register should be configured, however this driver
- * deligates this task to userspace applications due to a restriction that this
- * register is write-only and the other bits have own effects.
- *
- * Unlike Fireface 800, Fireface 400 cancels transferring asynchronous
- * transactions when the 1st and 2nd of the register stand. These two bits have
- * the same effect.
- * - 0x02, 0x01: cancel transferring
- *
- * On the other hand, the bits have no effect on Fireface 800. This model
- * cancels asynchronous transactions when the higher 4 bytes of address is
- * overwritten with zero.
- */
+// Controllers are allowed to register higher 4 bytes of destination address to
+// receive asynchronous transactions for MIDI messages, while the way to
+// register lower 4 bytes of address is different depending on protocols. For
+// details, please refer to comments in protocol implementations.
+//
+// This driver expects userspace applications to configure registers for the
+// lower address because in most cases such registers has the other settings.
int snd_ff_transaction_reregister(struct snd_ff *ff)
{
struct fw_card *fw_card = fw_parent_device(ff->unit)->card;