v2 of this driver submission builds and runs cleanly against Greg KH's
tty-next and (hopefully) addresses the concerns raised regarding the
dependence on tty_buffer internals; specifically with the workarounds to fix
1) data loss on hangup and 2) throttling before the flip buffers are full.
1) Data loss on hangup
Although I experimented with alternative solutions as Alan suggested, none
were practical. For example, this sequence (which is almost identical to
what the n_tty ldisc does in input_available_p()):
tty_flush_to_ldisc(tty);
n = ldisc->ops->chars_in_buffer(tty);
suffers from a race that the ldisc could have _just_ emptied the read
buffer between these calls, so that n == 0 but data is still in the
flip buffers.
For now, the driver v2 delays the hangup on carrier loss by a fixed timeout.
2) Flip buffers full before throttle received from ldisc
Because driver throttling is performed by the ldisc, and not by the
tty_buffer, the flip buffers can be filled before receiving a throttle
request.
For now, the driver v2 pre-buffers in front of the tty_buffer; ie, rx data
which is not accepted by tty_insert_flip_string...() is buffered in the
driver, the sender is throttled and when ldisc unthrottles, normal operation
resumes by feeding the tty_buffer from the pre-buffered data.
This driver v2 also fixes the occasionally flaky auto-connect, 2 (valid)
lockdep warnings, racy line status changes, and delays fifo allocation
until .activate() to minimize memory footprint.
As before, the TODO file notes the remaining issues.
Regards,
Peter
Peter Hurley (1):
staging: fwserial: Add TTY-over-Firewire serial driver
drivers/staging/Kconfig | 2 +
drivers/staging/Makefile | 1 +
drivers/staging/fwserial/Kconfig | 9 +
drivers/staging/fwserial/Makefile | 2 +
drivers/staging/fwserial/TODO | 37 +
drivers/staging/fwserial/dma_fifo.c | 310 ++++
drivers/staging/fwserial/dma_fifo.h | 130 ++
drivers/staging/fwserial/fwserial.c | 2946 +++++++++++++++++++++++++++++++++++
drivers/staging/fwserial/fwserial.h | 387 +++++
9 files changed, 3824 insertions(+)
create mode 100644 drivers/staging/fwserial/Kconfig
create mode 100644 drivers/staging/fwserial/Makefile
create mode 100644 drivers/staging/fwserial/TODO
create mode 100644 drivers/staging/fwserial/dma_fifo.c
create mode 100644 drivers/staging/fwserial/dma_fifo.h
create mode 100644 drivers/staging/fwserial/fwserial.c
create mode 100644 drivers/staging/fwserial/fwserial.h
--
1.7.12.3
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