On Friday 26 November 2021 09:39:18 Loic Poulain wrote:
Hi Pali,
On Thu, 25 Nov 2021 at 19:10, Pali Rohár pali@kernel.org wrote:
On Thursday 25 November 2021 18:16:15 Loic Poulain wrote:
Add support for CDC ACM using the new UDC and gadget API. This protocol can be used for serial over USB data transfer and is widely supported by various OS (GNU/Linux, MS-Windows, OSX...). The usual purpose of such link is to access device debug console and can be useful for products not exposing regular UART to the user.
A default stdio device named 'usbacm' is created, and can be used to redirect console to USB link over CDC ACM:
setenv stdin usbacm; setenv stdout usbacm
Signed-off-by: Loic Poulain loic.poulain@linaro.org
v2: - remove possible infinite recursipe print loop - Remove acmconsole command, start function along the stdio device v3: - Use __constant_cpu_to_le16() when possible - Rename stdio dev to 'usbacm' - Rename init function to drv_usbacm_init
Hello! Just one question: is in this v3 patch fixed stdout-only configuration, or it still has a bug which you described in email? https://lore.kernel.org/u-boot/CAMZdPi8185pAiO4w2QYMtWGAFJiX=eJ_BJW1CusRE990...
Because neither in above change long nor in driver help description nor in driver source code is any comment related to stdout-only device.
No, actually it ended not being an issue, we can have it stdout/stdin independently. The driver loops on 'irq'-handling to ensure the USB controller has completely flushed TX before returning.
This is probably suboptimal, but important is that there is no such issue. So it means that this new code can be replacement for old usbtty, which is really nice!!
Note that stdout-only does not have to be too uncommon. For example Nokia N900 has enabled UART, keyboard+lcd and usbtty by default and sometimes I enabled input only from keyboard and looked at usbtty terminal (as stdout-only) if everything is working fine (that every pressed key on keyboard was echoed correctly back to usbtty).
Yes, checked this case on a imx7d based board and stdout-only works as you describe.
Regards, Loic