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Date: Sun, 26 Apr 2026 21:16:05 +0200
From: Greg KH <gregkh@linuxfoundation.org>
To: Debjeet Banerjee <debjeetbanerjee48@gmail.com>
Cc: dtwlin@gmail.com, johan@kernel.org, elder@kernel.org,
	greybus-dev@lists.linaro.org, linux-staging@lists.linux.dev,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] staging: greybus: uart: document c_cflag handling in
 set_termios
Message-ID: <2026042618-whole-cassette-b15e@gregkh>
References: <20260419032632.35351-1-debjeetbanerjee48@gmail.com>
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In-Reply-To: <20260419032632.35351-1-debjeetbanerjee48@gmail.com>

On Sun, Apr 19, 2026 at 08:56:32AM +0530, Debjeet Banerjee wrote:
> gb_tty_set_termios() derives UART line configuration from a subset of
> termios->c_cflag bits, namely CSIZE, CSTOPB, PARENB, PARODD, CMSPAR,
> CRTSCTS, CLOCAL and CBAUD. Other c_cflag bits are not interpreted by
> the driver and are not represented in the Greybus UART protocol
> messages.
> 
> The existing FIXME suggests clearing unsupported bits from termios.
> However, the driver already limits its behavior to the supported subset
> when constructing line coding, and unused bits are effectively ignored.
> No invalid or unsupported values are propagated to the hardware.
> 
> Replace the FIXME with a comment documenting which c_cflag bits are
> consumed by the driver and clarifying that other bits are ignored.

Ignoring is fine, but shouldn't the bits be cleared to let userspace
know about this?  I think that's why we wrote that FIXME all so long
ago.

thanks,

greg k-h