linux-kernel - Re: [PATCH] Documentation: devices.txt: reconcile serial/ucc

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Message-ID: <10fbf60c-f7fe-d2ca-3d16-488453a88889@infradead.org>
Date:   Tue, 25 Jul 2023 13:51:37 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Timur Tabi <timur@...nel.org>
Cc:     linux-kernel@...r.kernel.org,
        Kumar Gala <galak@...nel.crashing.org>,
        linuxppc-dev@...ts.ozlabs.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        linux-serial@...r.kernel.org, Jonathan Corbet <corbet@....net>,
        linux-doc@...r.kernel.org
Subject: Re: [PATCH] Documentation: devices.txt: reconcile serial/ucc_uart
 minor numers



On 7/25/23 13:38, Timur Tabi wrote:
> On Mon, Jul 24, 2023 at 1:33 AM Randy Dunlap <rdunlap@...radead.org> wrote:
>>
>> Reconcile devices.txt with serial/ucc_uart.c regarding device number
>> assignments. ucc_uart.c supports 4 ports and uses minor devnums
>> 46-49, so update devices.txt with that info.
>> Then update ucc_uart.c's reference to the location of the devices.txt
>> list in the kernel source tree.
>>
>> Fixes: d7584ed2b994 ("[POWERPC] qe-uart: add support for Freescale QUICCEngine UART")
>> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
>> Signed-off-by: Randy Dunlap <rdunlap@...radead.org>
>> Cc: Timur Tabi <timur@...nel.org>
>> Cc: Kumar Gala <galak@...nel.crashing.org>
>> Cc: linuxppc-dev@...ts.ozlabs.org
>> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>> Cc: Jiri Slaby <jirislaby@...nel.org>
>> Cc: linux-serial@...r.kernel.org
>> Cc: Jonathan Corbet <corbet@....net>
>> Cc: linux-doc@...r.kernel.org
> 
> Acked-by: Timur Tabi <timur@...nel.org>
> 
> One thing does concern me.  The UCC UART driver piggy-backs on the CPM
> driver's layout (see cpm_uart.h), but apparently CPM UART supports 6
> devices, not four:
> 
> #define UART_NR        fs_uart_nr
> 
> where fs_uart_nr is defined in enum fs_uart_id.
> 
> Unfortunately, it's been so long since I've touched this code, I'm not
> sure whether this means anything.

If CPM UART code ever worked with > 4 ports, it probably just used minor devnums
that were not allocated to it.

Also, it looks like the CPU UART part of Documentation/admin-guide/devices.txt
needs to be updated:

		 46 = /dev/cucpm0		Callout device for ttyCPM0
		    ...
		 49 = /dev/cucpm5		Callout device for ttyCPM5

The driver must use some tricks to get 6 ports into 4 devnums. :)


-- 
~Randy