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

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

[Konstantin Shkolnyy]

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@gmail.com>
---
change in v3: Presented new function addition as a separate patch #1,
to simplify code review.

 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);
+		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 {
+		dev_err(&port->dev, "failed get req 0x%x size %d status: %d\n",
+				req, bufsize, result);
+		if (result >= 0)
+			result = -EPROTO;
+
+		/*
+		 * FIXME Some callers don't bother to check for error,
+		 * at least give them consistent junk until they are fixed
+		 */
+		memset(buf, 0, bufsize);
+	}
+
+	kfree(dmabuf);
+
+	return result;
+}
+
+/*
+ * Reads any 32-bit CP210X_ register identified by req.
+ */
+static int cp210x_read_u32_reg(struct usb_serial_port *port, u8 req, u32 *val)
+{
+	__le32 le32_val;
+	int err;
+
+	err = cp210x_read_reg_block(port, req, &le32_val, sizeof(le32_val));
+	if (err) {
+		/*
+		 * FIXME Some callers don't bother to check for error,
+		 * at least give them consistent junk until they are fixed
+		 */
+		*val = 0;
+		return err;
+	}
+
+	*val = le32_to_cpu(le32_val);
+
+	return 0;
+}
+
+/*
+ * Reads any 16-bit CP210X_ register identified by req.
+ */
+static int cp210x_read_u16_reg(struct usb_serial_port *port, u8 req, u16 *val)
+{
+	__le16 le16_val;
+	int err;
+
+	err = cp210x_read_reg_block(port, req, &le16_val, sizeof(le16_val));
+	if (err)
+		return err;
+
+	*val = le16_to_cpu(le16_val);
+
+	return 0;
+}
+
+/*
+ * Reads any 8-bit CP210X_ register identified by req.
+ */
+static int cp210x_read_u8_reg(struct usb_serial_port *port, u8 req, u8 *val)
+{
+	return cp210x_read_reg_block(port, req, val, sizeof(*val));
+}
+
+/*
+ * Writes any 16-bit CP210X_ register (req) whose value is passed
+ * entirely in the wValue field of the USB request.
+ */
+static int cp210x_write_u16_reg(struct usb_serial_port *port, u8 req, u16 val)
+{
+	struct usb_serial *serial = port->serial;
+	struct cp210x_port_private *port_priv = usb_get_serial_port_data(port);
+	int result;
+
+	result = usb_control_msg(serial->dev, usb_sndctrlpipe(serial->dev, 0),
+			req, REQTYPE_HOST_TO_INTERFACE, val,
+			port_priv->bInterfaceNumber, NULL, 0,
+			USB_CTRL_SET_TIMEOUT);
+	if (result < 0) {
+		dev_err(&port->dev, "failed set request 0x%x status: %d\n",
+				req, result);
+	}
+
+	return result;
+}
+
+/*
+ * Writes a variable-sized block of CP210X_ registers, identified by req.
+ * Data in buf must be in native USB byte order.
+ */
+static int cp210x_write_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)
+		return -ENOMEM;
+
+	memcpy(dmabuf, buf, bufsize);
+
+	result = usb_control_msg(serial->dev, usb_sndctrlpipe(serial->dev, 0),
+			req, REQTYPE_HOST_TO_INTERFACE, 0,
+			port_priv->bInterfaceNumber, dmabuf, bufsize,
+			USB_CTRL_SET_TIMEOUT);
+
+	kfree(dmabuf);
+
+	if (result == bufsize) {
+		result = 0;
+	} else {
+		dev_err(&port->dev, "failed set req 0x%x size %d status: %d\n",
+				req, bufsize, result);
+		if (result >= 0)
+			result = -EPROTO;
+	}
+
+	return result;
+}
+
+/*
+ * Writes any 32-bit CP210X_ register identified by req.
+ */
+static int cp210x_write_u32_reg(struct usb_serial_port *port, u8 req, u32 val)
+{
+	__le32 le32_val;
+
+	le32_val = cpu_to_le32(val);
+
+	return cp210x_write_reg_block(port, req, &le32_val, sizeof(le32_val));
+}
+
+/*
  * cp210x_get_config
  * Reads from the CP210x configuration registers
  * 'size' is specified in bytes.
-- 
1.8.4.5

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

[Johan Hovold]

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@gmail.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

RE: [PATCH v3 1/4 RESEND] USB: serial: cp210x: New register access functions.

[Konstantin Shkolnyy]

> -----Original Message-----
> From: linux-usb-owner@vger.kernel.org [mailto:linux-usb-
> owner@vger.kernel.org] On Behalf Of Johan Hovold
> Sent: Monday, January 18, 2016 11:33
> To: Konstantin Shkolnyy
> Cc: johan@kernel.org; linux-usb@vger.kernel.org; linux-
> kernel@vger.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@gmail.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.

I did split 8, 16 and 32 into 3 patches in v2, then it seemed to me it would be easier to review if I also separated new functions.
I can just use an amended v2 as v4.

I add reads and writes together to avoid type mismatches in the code that reads/writes the same variable,

> >  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),

The current cp210x_get_config() does clear the caller's storage on an error. So my refactoring just preserves the old behavior.

> how about adding the missing error handling first?

It's easier to work with and see bugs in cleaned up code, that's why I do it in this order.
I do intend to fix the error handling later.

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

[Johan Hovold]

On Mon, Jan 18, 2016 at 07:59:48PM +0000, Konstantin Shkolnyy wrote:
> > -----Original Message-----
> > From: linux-usb-owner@vger.kernel.org [mailto:linux-usb-
> > owner@vger.kernel.org] On Behalf Of Johan Hovold
> > Sent: Monday, January 18, 2016 11:33
> > To: Konstantin Shkolnyy
> > Cc: johan@kernel.org; linux-usb@vger.kernel.org; linux-
> > kernel@vger.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@gmail.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.
> 
> I did split 8, 16 and 32 into 3 patches in v2, then it seemed to me it
> would be easier to review if I also separated new functions.
> I can just use an amended v2 as v4.

Sounds good.

> I add reads and writes together to avoid type mismatches in the code
> that reads/writes the same variable,

Probably makes sense.

> > >  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),
> 
> The current cp210x_get_config() does clear the caller's storage on an
> error. So my refactoring just preserves the old behavior.

Ah, the current code only fails to clear the callers storage on
allocation errors. Then I guess it's ok to fix up the call sites after.

> > how about adding the missing error handling first?
> 
> It's easier to work with and see bugs in cleaned up code, that's why I
> do it in this order.
> I do intend to fix the error handling later.

Sounds good.

Thanks,
Johan