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This commit is contained in:
Gregory Nutt 2016-07-26 12:13:30 -06:00
parent 084d200a66
commit 0c7f5d62e4
1 changed files with 46 additions and 5 deletions
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51
drivers/serial/pty.c
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@ -33,6 +33,42 @@
*
****************************************************************************/
/* TODO: O_NONBLOCK is not yet supported. Currently, the pipes are opened
* nonblocking so only blocking behavior is supported. This driver must be
* able to support multiple clients that have have a PTY device opened in
* blocking and non-blocking modes simultaneously.
*
* There are two different possible implementations under consideration:
*
* 1. Keep the pipes in blockingmode, but use a test based on FIONREAD (for
* the source pipe) or FIONSPACE (for the sink pipe) to determine if the
* read or write would block. There is existing logic like this in
* pty_read() to handle the case of a single byte reads which must never
* block in any case: Essentially, this logic uses FIONREAD to determine
* if there is anything to read before calling file_read(). Similar
* logic could be replicated for all read cases.
*
* Analogous logic could be added for all writes using FIONSPACE to
* assure that there is sufficient free space in the sink pipe to write
* without blocking. The write length could be adjusted, in necceary,
* to assure that there is no blocking.
*
* Locking, perhaps via sched_lock(), would be required to assure the
* test via FIONREAD or FIONWRITE is atomic with respect to the
* file_read() or file_write() operation.
*
* 2. An alternative that appeals to me is to modify the contained source
* or sink pipe file structures before each file_read() or file_write()
* operation to assure that the O_NONBLOCK is set correctly when the
* pipe read or write operation is performed.
*
* This would require (1) the ability to lock each pipe individually,
* setting the blocking mode for the source or sing pipe to match the
* mode in the open flags of the PTY device, and (2) logic to restore
* the default pipe mode after the file_read/write() operation and
* before the pipe is unlocked.
*/
/****************************************************************************
* Included Files
****************************************************************************/
@ -492,7 +528,8 @@ static ssize_t pty_read(FAR struct file *filep, FAR char *buffer, size_t len)
*
* REVISIT: Should not block if the oflags include O_NONBLOCK.
* How would we ripple the O_NONBLOCK characteristic to the
* contained soruce pipe? file_fcntl()?
* contained soruce pipe? file_fcntl()? Or FIONREAD? See the
* TODO comment at the top of this file.
*/
nread = file_read(&dev->pd_src, &ch, 1);
@ -544,7 +581,8 @@ static ssize_t pty_read(FAR struct file *filep, FAR char *buffer, size_t len)
*
* REVISIT: Should not block if the oflags include O_NONBLOCK.
* How would we ripple the O_NONBLOCK characteristic to the
* contained source pipe? file_fcntl()?
* contained source pipe? file_fcntl()? Or FIONREAD? See the
* TODO comment at the top of this file.
*/
ntotal = file_read(&dev->pd_src, buffer, len);
@ -610,7 +648,8 @@ static ssize_t pty_write(FAR struct file *filep, FAR const char *buffer, size_t
*
* REVISIT: Should not block if the oflags include O_NONBLOCK.
* How would we ripple the O_NONBLOCK characteristic to the
* contained sink pipe? file_fcntl()?
* contained sink pipe? file_fcntl()? Or FIONSPACE? See the
* TODO comment at the top of this file.
*/
nwritten = file_write(&dev->pd_sink, &cr, 1);
@ -630,7 +669,8 @@ static ssize_t pty_write(FAR struct file *filep, FAR const char *buffer, size_t
*
* REVISIT: Should not block if the oflags include O_NONBLOCK.
* How would we ripple the O_NONBLOCK characteristic to the
* contained sink pipe? file_fcntl()?
* contained sink pipe? file_fcntl()? Or FIONSPACe? See the
* TODO comment at the top of this file.
*/
nwritten = file_write(&dev->pd_sink, &ch, 1);
@ -653,7 +693,8 @@ static ssize_t pty_write(FAR struct file *filep, FAR const char *buffer, size_t
*
* REVISIT: Should not block if the oflags include O_NONBLOCK.
* How would we ripple the O_NONBLOCK characteristic to the
* contained sink pipe? file_fcntl()?
* contained sink pipe? file_fcntl()? Or FIONSPACE? See the
* TODO comment at the top of this file.
*/
ntotal = file_write(&dev->pd_sink, buffer, len);