On 2024-08-01, Jocelyn Falempe <jfalempe@xxxxxxxxxx> wrote:
> * It uses a circular buffer so the console->write() callback is very
> quick, and will never stall.
> * Drawing is done asynchronously using a workqueue.
For CON_NBCON, neither of the above points are necessary. You can draw
directly from the write_thread() callback. See below:
> +static bool drm_log_work_draw(void)
> +{
> + unsigned int len;
> + char buf[512];
> +
> + len = drm_log_buf_read(buf, sizeof(buf));
> + if (len)
> + drm_log_draw_all(buf, len);
> + return len != 0;
> +}
For CON_NBCON, this is essentially your write_thread() callback:
void drm_log_write_thread(struct console *con,
struct nbcon_write_context *wctxt)
{
drm_log_draw_all(wctxt->outbuf, wctxt->len);
}
You cannot implement a write_atomic() callback because the console must
be able to print directly in NMI context and must not defer. But
write_atomic() is optional, so you should be fine there.
Disclaimer: Only in PREEMPT_RT patchset at the moment.
John Ogness
