linux-kernel - Re: [PATCH V2 4/4] USB: serial: f81232: fix bulk

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Date:   Wed, 5 Sep 2018 16:46:28 +0200
From:   Johan Hovold <johan@...nel.org>
To:     "Ji-Ze Hong (Peter Hong)" <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, hpeter+linux_kernel@...il.com
Subject: Re: [PATCH V2 4/4] USB: serial: f81232: fix bulk_in/out size

On Thu, Aug 30, 2018 at 09:47:14AM +0800, Ji-Ze Hong (Peter Hong) wrote:
> Fix Fintek F81232 bulk_in/out size to 64/16 according to the spec.
> http://html.alldatasheet.com/html-pdf/406315/FINTEK/F81232/1762/8/F81232.html

I know we've discussed this before, but please explain here in the
commit message why you want to do this.

The bulk_in/out_size fields only set the buffer sizes used by the
driver and using buffers larger than the endpoint size is typically only
more efficient even if there may be hardware reasons for not wanting to
use that.

You said last time, you datasheets were incorrect and that the devices
were in fact using 64 b endpoints, right?

> Signed-off-by: Ji-Ze Hong (Peter Hong) <hpeter+linux_kernel@...il.com>
> ---
>  drivers/usb/serial/f81232.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/serial/f81232.c b/drivers/usb/serial/f81232.c
> index 863430d7535f..e3ab1646a693 100644
> --- a/drivers/usb/serial/f81232.c
> +++ b/drivers/usb/serial/f81232.c
> @@ -785,8 +785,7 @@ static struct usb_serial_driver f81232_device = {
>  	},
>  	.id_table =		id_table,
>  	.num_ports =		1,
> -	.bulk_in_size =		256,
> -	.bulk_out_size =	256,
> +	.bulk_out_size =	16,
>  	.open =			f81232_open,
>  	.close =		f81232_close,
>  	.dtr_rts =		f81232_dtr_rts,

Johan