linux-kernel - Re: [PATCH v3 1/4 RESEND] USB: serial: cp210x: New register access functions.

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Date:	Mon, 18 Jan 2016 18:32:36 +0100
From:	Johan Hovold <johan@...nel.org>
To:	Konstantin Shkolnyy <konstantin.shkolnyy@...il.com>
Cc:	johan@...nel.org, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/4 RESEND] USB: serial: cp210x: New register access
 functions.

On Sat, Jan 16, 2016 at 01:46:24PM -0600, Konstantin Shkolnyy wrote:
> cp210x_get_config and cp210x_set_config are cumbersome to use. This change
> introduces new register access functions to replace them. New functions
> are not yet called - the switch is done gradually in following changes.
> 
> Signed-off-by: Konstantin Shkolnyy <konstantin.shkolnyy@...il.com>
> ---
> change in v3: Presented new function addition as a separate patch #1,
> to simplify code review.

Thanks for the v3.

You should not be adding (static) functions before they have a caller as
this generates compiler warnings.

Please define the new helper functions when converting their call
sites. You can split the 8, 16 and 32-bit helpers in separate patches and
possibly also separate read and write if that makes sense in order to
keep the diffs smaller.

>  drivers/usb/serial/cp210x.c | 166 ++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 166 insertions(+)
> 
> diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c
> index fd67958..324eb7e 100644
> --- a/drivers/usb/serial/cp210x.c
> +++ b/drivers/usb/serial/cp210x.c
> @@ -323,6 +323,172 @@ struct cp210x_comm_status {
>  #define PURGE_ALL		0x000f
>  
>  /*
> + * Reads a variable-sized block of CP210X_ registers, identified by req.
> + * Returns data into buf in native USB byte order.
> + */
> +static int cp210x_read_reg_block(struct usb_serial_port *port, u8 req,
> +		void *buf, int bufsize)
> +{
> +	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) {
> +		/*
> +		 * FIXME Some callers don't bother to check for error,
> +		 * at least give them consistent junk until they are fixed
> +		 */
> +		memset(buf, 0, bufsize);

Instead of adding these FIXMEs and possibly risk introducing regressions
(these functions used to leave the previous values unchanged on errors),
how about adding the missing error handling first?

> +		return -ENOMEM;
> +	}

Thanks,
Johan