ssize_t rtlx_write(int index, const void __user *buffer, size_t count)
{
struct rtlx_channel *rt;
unsigned long failed;
size_t rt_read;
size_t fl;
if (rtlx == NULL)
return(-ENOSYS);
rt = &rtlx->channel[index];
mutex_lock(&channel_wqs[index].mutex);
smp_rmb();
rt_read = rt->rt_read;
/* total number of bytes to copy */
count = min(count, (size_t)write_spacefree(rt_read, rt->rt_write,
rt->buffer_size));
/* first bit from write pointer to the end of the buffer, or count */
fl = min(count, (size_t) rt->buffer_size - rt->rt_write);
failed = copy_from_user(rt->rt_buffer + rt->rt_write, buffer, fl);
if (failed)
goto out;
/* if there's any left copy to the beginning of the buffer */
if (count - fl) {
failed = copy_from_user(rt->rt_buffer, buffer + fl, count - fl);
}
out:
count -= failed;
smp_wmb();
rt->rt_write = (rt->rt_write + count) % rt->buffer_size;
smp_wmb();
mutex_unlock(&channel_wqs[index].mutex);
return count;
}
unsigned int rtlx_write_poll(int index)
{
struct rtlx_channel *chan = &rtlx->channel[index];
return write_spacefree(chan->rt_read, chan->rt_write, chan->buffer_size);
}