From c59dbcadd5d125ba40595612dc91ab18924164d3 Mon Sep 17 00:00:00 2001 From: Jeff Dike Date: Tue, 16 Oct 2007 01:26:42 -0700 Subject: uml: fix console writing bugs The previous console cleanup patch switched generic_read and generic_write from calling os_{read,write}_file to calling read and write directly. Because the calling convention is different, they now need to get any error from errno rather than the return value. I did this for generic_read, but forgot about generic_write. While chasing some output corruption, I noticed that line_write was unnecessarily calling flush_buffer, and deleted it. I don't understand why, but the corruption disappeared. This is unneeded because there already is a perfectly good mechanism for finding out when the host output device has some room to write data - there is an interrupt that comes in when writes can happen again. line_write calling flush_buffer seemed to just be an attempt to opportunistically get some data out to the host. I also made write_chan short-circuit calling into the host-level code for zero-length writes. Calling libc write with a length of zero conflated write not being able to write anything with asking it not to write anything. Better to just cut it off as soon as possible. Signed-off-by: Jeff Dike Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/um/drivers/chan_user.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) (limited to 'arch/um/drivers/chan_user.c') diff --git a/arch/um/drivers/chan_user.c b/arch/um/drivers/chan_user.c index 77557e233f5..d29e56d8ced 100644 --- a/arch/um/drivers/chan_user.c +++ b/arch/um/drivers/chan_user.c @@ -38,7 +38,16 @@ int generic_read(int fd, char *c_out, void *unused) int generic_write(int fd, const char *buf, int n, void *unused) { - return write(fd, buf, n); + int err; + + err = write(fd, buf, n); + if (err > 0) + return err; + else if (errno == EAGAIN) + return 0; + else if (err == 0) + return -EIO; + return -errno; } int generic_window_size(int fd, void *unused, unsigned short *rows_out, -- cgit v1.2.3