From: Johan Hovold <johan@kernel.org>
To: Himadri Pandya <himadrispandya@gmail.com>
Cc: gregkh@linuxfoundation.org, linux-usb@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 2/6] USB: serial: cp210x: use usb_control_msg_recv() and usb_control_msg_send()
Date: Tue, 21 Sep 2021 13:34:57 +0200 [thread overview]
Message-ID: <YUnDYWWhEUpnMq7R@hovoldconsulting.com> (raw)
In-Reply-To: <20210801203122.3515-3-himadrispandya@gmail.com>
On Mon, Aug 02, 2021 at 02:01:18AM +0530, Himadri Pandya wrote:
> The new wrapper functions for usb_control_msg() can accept data from
> stack with robust error checks.
Please rephrase the "robust error checks" along the lines of "treats
short reads as an error".
> Hence use the wrappers with stack
> variables for usb transfer buffers to save kernel memory.
Again, you're not saving memory here, just moving the allocation.
> Signed-off-by: Himadri Pandya <himadrispandya@gmail.com>
> ---
> Changes in v2:
> - Drop unrelated style fixes
> ---
> drivers/usb/serial/cp210x.c | 107 ++++++++++--------------------------
> 1 file changed, 30 insertions(+), 77 deletions(-)
>
> diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c
> index 3c80bfbf3bec..b73581fc1768 100644
> --- a/drivers/usb/serial/cp210x.c
> +++ b/drivers/usb/serial/cp210x.c
> @@ -628,29 +628,18 @@ static int cp210x_read_reg_block(struct usb_serial_port *port, u8 req,
> {
> struct usb_serial *serial = port->serial;
> struct cp210x_port_private *port_priv = usb_get_serial_port_data(port);
> - void *dmabuf;
> int result;
>
> - dmabuf = kmalloc(bufsize, GFP_KERNEL);
> - if (!dmabuf)
> - return -ENOMEM;
> -
> - result = usb_control_msg(serial->dev, usb_rcvctrlpipe(serial->dev, 0),
> - req, REQTYPE_INTERFACE_TO_HOST, 0,
> - port_priv->bInterfaceNumber, dmabuf, bufsize,
> - USB_CTRL_SET_TIMEOUT);
> - if (result == bufsize) {
> - memcpy(buf, dmabuf, bufsize);
> - result = 0;
> - } else {
> + result = usb_control_msg_recv(serial->dev, 0, req,
> + REQTYPE_INTERFACE_TO_HOST, 0,
> + port_priv->bInterfaceNumber, buf,
> + bufsize, USB_CTRL_SET_TIMEOUT,
> + GFP_KERNEL);
> + if (result) {
> dev_err(&port->dev, "failed get req 0x%x size %d status: %d\n",
> req, bufsize, result);
This will also no longer log the length of short reads. Please at least
mention it in the commit message.
> - if (result >= 0)
> - result = -EIO;
> }
>
> - kfree(dmabuf);
> -
> return result;
> }
Johan
next prev parent reply other threads:[~2021-09-21 11:35 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-01 20:31 [PATCH v2 0/6] USB: serial: use wrappers for usb_control_msg() Himadri Pandya
2021-08-01 20:31 ` [PATCH v2 1/6] USB: serial: ch314: use usb_control_msg_recv() and usb_control_msg_send() Himadri Pandya
2021-09-21 11:26 ` Johan Hovold
2021-08-01 20:31 ` [PATCH v2 2/6] USB: serial: cp210x: " Himadri Pandya
2021-09-21 11:34 ` Johan Hovold [this message]
2021-08-01 20:31 ` [PATCH v2 3/6] USB: serial: f81232: " Himadri Pandya
2021-09-21 12:06 ` Johan Hovold
2021-08-01 20:31 ` [PATCH v2 4/6] USB: serial: ftdi_sio: use usb_control_msg_recv() Himadri Pandya
2021-09-21 12:17 ` Johan Hovold
2021-08-01 20:31 ` [PATCH v2 5/6] USB: serial: keyspan_pda: " Himadri Pandya
2021-09-21 12:27 ` Johan Hovold
2021-08-01 20:31 ` [PATCH v2 6/6] USB: serial: kl5kusb105: use usb_control_msg_recv() and usb_control_msg_send() Himadri Pandya
2021-09-21 12:41 ` Johan Hovold
2021-09-26 13:00 ` Himadri Pandya
2021-09-21 11:10 ` [PATCH v2 0/6] USB: serial: use wrappers for usb_control_msg() Johan Hovold
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