On 01/08/2024 12:51, John Ogness wrote:
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.
Thanks, so that means the circular buffer and workqueue are only necessary until write_thread() is merged in mainline. It will be a nice simplification. I think I can also register one console for each drm driver, which will simplify drm_log even further. (currently it would mean having a circular buffer and work function for each driver which is a bit too much).
Do you know if there is a chance to have write_thread() in 6.12 or 6.13 ?
John Ogness >
Best regards -- Jocelyn
