linux-kernel - Re: [PATCH v2] USB: serial: cp210x: Add tx

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Message-ID: <CAHp75VcU5YeB3YMfk8JrmhJVjFCZ0ity6eACefkK1kQVTyJStQ@mail.gmail.com>
Date:	Wed, 25 Nov 2015 22:26:12 +0200
From:	Andy Shevchenko <andy.shevchenko@...il.com>
To:	Konstantin Shkolnyy <konstantin.shkolnyy@...il.com>
Cc:	johan@...nel.org, USB <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] USB: serial: cp210x: Add tx_empty()

On Wed, Nov 25, 2015 at 12:28 AM, Konstantin Shkolnyy
<konstantin.shkolnyy@...il.com> wrote:
> Added tx_empty callback needed for generic wait-until-sent support.
> Without this function, when the port is closed usbserial can't know that
> there are still data in the chip's transmit FIFO. The chip gets disabled
> and untransmitted data lost. When the actual byte count is reported by
> tx-empty the close can be delayed until all data are sent.
>

>  /*
> + * Read how many bytes are waiting in the TX queue.
> + */

One line?

> +static bool cp210x_tx_empty(struct usb_serial_port *port)
> +{
> +       int err;
> +       u32 count;
> +
> +       err = cp210x_get_tx_queue_byte_count(port, &count);

> +       if (!err && count)
> +               return false;
> +
> +       return true;

return err || !count;

Btw, can be count left uninitialized?

-- 
With Best Regards,
Andy Shevchenko
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