linux-kernel - Re: [TRIVIAL PATCH] usb/serial.h: Increase max number of serial ports per USB-serial device

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Message-ID: <20150703082825.GA6637@localhost>
Date:	Fri, 3 Jul 2015 10:28:25 +0200
From:	Johan Hovold <johan@...nel.org>
To:	Bartosz Tomeczko <bartosz.tomeczko@...il.com>
Cc:	Johan Hovold <johan@...nel.org>, linux-kernel@...r.kernel.org,
	trivial@...nel.org
Subject: Re: [TRIVIAL PATCH] usb/serial.h: Increase max number of serial
 ports per USB-serial device

On Thu, Jul 02, 2015 at 05:13:47PM +0200, Bartosz Tomeczko wrote:
> Hello,
> 
> I am using MOXA USB-to-serial converter with 16 serial ports. This
> device is namely a MOXA UPort 1650-16. This device works as a simple
> usb-serial adapter and therefore its driver uses
> include/linux/usb/serial.h file. In this very file however maximal
> number of serial ports served by the driver is eight (MAX_NUM_PORTS).
> I would like to propose a trivial patch which would allow MOXA users
> to use all ports of the device instead of just having eight of them
> usable (as it is right now). Trivial change which might be applied on
> the top of (4da3064d1775810f10f7ddc1c34c3f1ff502a654) is as follows:
> 
> diff --git a/include/linux/usb/serial.h b/include/linux/usb/serial.h
> index 704a1ab..b7af736 100644
> --- a/include/linux/usb/serial.h
> +++ b/include/linux/usb/serial.h
> @@ -20,7 +20,7 @@
>  #include <linux/kfifo.h>
> 
>  /* The maximum number of ports one device can grab at once */
> -#define MAX_NUM_PORTS          8
> +#define MAX_NUM_PORTS          16
> 
>  /* parity check flag */
>  #define RELEVANT_IFLAG(iflag)  (iflag & (IGNBRK|BRKINT|IGNPAR|PARMRK|INPCK))

I'm aware that this limit is too low be able to use all ports on that
Moxa device. I have some patches lying around that I never got to finish
that clean up the descriptor handling and removes the arbitrary port
limitation completely.

Let me revisit those, and I'll make sure this gets fixed for 4.3.

Thanks,
Johan
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