linux-kernel - Re: [PATCH V2 1/1] usb:serial:f81534 Add F81532/534 Driver

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Message-ID: <20150625080607.GA28464@localhost>
Date:	Thu, 25 Jun 2015 10:06:07 +0200
From:	Johan Hovold <johan@...nel.org>
To:	Peter Hung <hpeter@...il.com>
Cc:	johan@...nel.org, gregkh@...uxfoundation.org,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	peter_hong@...tek.com.tw, tom_tsai@...tek.com.tw,
	Peter Hung <hpeter+linux_kernel@...il.com>
Subject: Re: [PATCH V2 1/1] usb:serial:f81534 Add F81532/534 Driver

Hi Peter,

On Thu, Jun 25, 2015 at 01:16:56PM +0800, Peter Hung wrote:
> Hello Johan,
> 
> Peter Hung 於 2015/6/15 上午 09:54 寫道:
> > This driver is for Fintek F81532/F81534 USB to Serial Ports IC.
> > 
> > Features:
> > 1. F81534 is 1-to-4 & F81532 is 1-to-2 serial ports IC
> > 2. Support Baudrate from B50 to B1500000 (excluding B1000000).
> > 3. The RTS signal can be transformed their behavior with configuration
> >     for transceiver (for RS232/RS485/RS422) (/sys/class/ttyUSBx/uart_mode)
> > 4. There are 4x3 output-only GPIOs to control transceiver mode. It's
> >     can be controlled via sysfs (/sys/class/ttyUSBx/gpio)
> > 
> 
> Do you receive my patch?

Yes, I did. I just haven't had time to review it yet.

> Are there anything should I do to improve it ?

There are, including

 - your custom read and write implementations look odd, you should be
   able to reuse a lot more of the generic framework
 - you'll also need to implement open/and close in some way
   (enable/disable in hardware or flag in software) as you should not
   push data to a closed tty
 - stack allocated buffers used for DMA (register accessors)
 - DMA buffers allocated as part of larger struct (read/write buffers)
 - lots of magic constants (e.g. use defines for the registers)
 - As Greg already mentioned, you need to implement gpio support using
   gpiolib, not a custom sysfs interface

I don't have time to look closer at the architectural bits until next
week I'm afraid, but perhaps you could start with the above.

Thanks,
Johan
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