linux-kernel - Re: [PATCH 1/2] USB: serial: ch341: fix lost character on LCR updates

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Message-ID: <863b4190-9b38-ed5a-0a18-74505702da21@kernel.org>
Date:   Wed, 31 Aug 2022 10:36:18 +0200
From:   Jiri Slaby <jirislaby@...nel.org>
To:     Johan Hovold <johan@...nel.org>,
        Jonathan Woithe <jwoithe@...t42.net>
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH 1/2] USB: serial: ch341: fix lost character on LCR updates

On 31. 08. 22, 10:15, Johan Hovold wrote:
> Disable LCR updates for pre-0x30 devices which use a different (unknown)
> protocol for line control and where the current register write causes
> the next received character to be lost.
> 
> Note that updating LCR using the INIT command has no effect on these
> devices either.
> 
> Reported-by: Jonathan Woithe <jwoithe@...t42.net>
> Link: https://lore.kernel.org/r/Ys1iPTfiZRWj2gXs@marvin.atrad.com.au
> Fixes: 4e46c410e050 ("USB: serial: ch341: reinitialize chip on reconfiguration")
> Fixes: 55fa15b5987d ("USB: serial: ch341: fix baud rate and line-control handling")
> Cc: stable@...r.kernel.org      # 4.10
> Signed-off-by: Johan Hovold <johan@...nel.org>
> ---
>   drivers/usb/serial/ch341.c | 10 +++++++++-
>   1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/serial/ch341.c b/drivers/usb/serial/ch341.c
> index 2798fca71261..2bcce172355b 100644
> --- a/drivers/usb/serial/ch341.c
> +++ b/drivers/usb/serial/ch341.c
> @@ -97,7 +97,10 @@ struct ch341_private {
>   	u8 mcr;
>   	u8 msr;
>   	u8 lcr;
> +
>   	unsigned long quirks;
> +	u8 version;

Could you move version above quirks? That would not create another 
7-byte padding in here. Actually it would not make ch341_private larger 
on 64bit at all, if I am looking correctly.

Other than that, looks good.

thanks,
-- 
js
suse labs