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2009-08-22 Roxana Leontie <roxana.leontie@gmail.com>

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* bsp_howto/framebuffer.t: documented the improvements made to
	read/write
This commit is contained in:
Joel Sherrill
2009-08-23 15:00:29 +00:00
parent b8dfc887f5
commit 2b86087062
2 changed files with 12 additions and 43 deletions
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50
doc/bsp_howto/framebuffer.t
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@@ -150,9 +150,7 @@ rtems_device_driver frame_buffer_close(
The @code{frame_buffer_read()} is invoked from a @code{read()} operation
on the frame buffer device.
Read functions should allow normal and partial reading at the end of frame buffer memory,
returning RTEMS_UNSATISFIED if trying to read beyond the frame buffer
memory or a negative number of bytes.
Read functions should allow normal and partial reading at the end of frame buffer memory.
This method returns RTEMS_SUCCESSFUL when the device is successfully read from:
@example
@@ -163,27 +161,10 @@ rtems_device_driver frame_buffer_read(
void *arg
)
@{
/*printk( "FBVGA read called.\n" );*/
rtems_libio_rw_args_t *rw_args = (rtems_libio_rw_args_t *)arg;
if ( (rw_args->offset >= fb_fix.smem_len) || (rw_args->count < 0) )@{
return RTEMS_UNSATISFIED;
@}
else
@{
/*partial reading*/
if ( (rw_args->offset + rw_args->count) > fb_fix.smem_len )@{
rw_args->count = fb_fix.smem_len - rw_args->offset;
memcpy(rw_args->buffer, (const void *) (rw_args->offset + fb_fix.smem_start), rw_args->count);
rw_args->bytes_moved = rw_args->count;
return RTEMS_SUCCESSFUL;
@}
/*best reading case*/
else@{
memcpy(rw_args->buffer, (const void *) (rw_args->offset + fb_fix.smem_start), rw_args->count);
rw_args->bytes_moved = rw_args->count;
return RTEMS_SUCCESSFUL;
@}
@}
rw_args->bytes_moved = ((rw_args->offset + rw_args->count) > fb_fix.smem_len ) ? (fb_fix.smem_len - rw_args->offset) : rw_args->count;
memcpy(rw_args->buffer, (const void *) (fb_fix.smem_start + rw_args->offset), rw_args->bytes_moved);
return RTEMS_SUCCESSFUL;
@}
@end group
@end example
@@ -206,27 +187,10 @@ rtems_device_driver frame_buffer_write(
void *arg
)
@{
/*printk( "FBVGA write called.\n" );*/
rtems_libio_rw_args_t *rw_args = (rtems_libio_rw_args_t *)arg;
if ( (rw_args->offset >= fb_fix.smem_len) || (rw_args->count < 0) )@{
return RTEMS_UNSATISFIED;
@}
else
@{
/*partial writing*/
if ( (rw_args->offset + rw_args->count) > fb_fix.smem_len )@{
rw_args->count = fb_fix.smem_len - rw_args->offset;
memcpy( (void *) (rw_args->offset + fb_fix.smem_start), rw_args->buffer, rw_args->count);
rw_args->bytes_moved = rw_args->count;
return RTEMS_SUCCESSFUL;
@}
/* best writing case*/
else@{
memcpy( (void *) (rw_args->offset + fb_fix.smem_start), rw_args->buffer, rw_args->count);
rw_args->bytes_moved = rw_args->count;
return RTEMS_SUCCESSFUL;
@}
@}
rw_args->bytes_moved = ((rw_args->offset + rw_args->count) > fb_fix.smem_len ) ? (fb_fix.smem_len - rw_args->offset) : rw_args->count;
memcpy( (void *) (fb_fix.smem_start + rw_args->offset), rw_args->buffer, rw_args->bytes_moved);
return RTEMS_SUCCESSFUL;
@}
@end group
@end example