[PATCH v2 0/4] Docs: usb: Code and text updates from usb-skeleton

[PATCH v2 0/4] Docs: usb: Code and text updates from usb-skeleton

[Philipp Hortmann]

Explanation and example code updates from usb-skeleton

v2: update patch #1 to #4
    - corrected format of function names like the following example:
      "`usb_bulk_msg` function" to "usb_bulk_msg()"

Philipp Hortmann (4):
  Docs: usb: update usb_bulk_msg receiving example
  Docs: usb: update comment and code near decrement our usage count for
    the device
  Docs: usb: update comment and code of function skel_delete
  Docs: usb: update explanation for device_present to disconnected

 .../driver-api/usb/writing_usb_driver.rst     | 73 +++++++++----------
 1 file changed, 35 insertions(+), 38 deletions(-)

-- 
2.25.1

[PATCH v2 1/4] Docs: usb: update usb_bulk_msg receiving example

[Philipp Hortmann]

Clarification that this example is not in the driver template anymore.
Update code example so that it fits best to usb-skeleton.c
Update format of function names

Signed-off-by: Philipp Hortmann <philipp.g.hortmann@gmail.com>
---
V1 -> V2: Added "Update format of function names" to patch description
          Corrected format of function names like the following example:
          "`usb_bulk_msg` function" to "usb_bulk_msg()"
---
 .../driver-api/usb/writing_usb_driver.rst     | 32 +++++++++----------
 1 file changed, 16 insertions(+), 16 deletions(-)

diff --git a/Documentation/driver-api/usb/writing_usb_driver.rst b/Documentation/driver-api/usb/writing_usb_driver.rst
index b43e1ce49f0e..ed11398837e5 100644
--- a/Documentation/driver-api/usb/writing_usb_driver.rst
+++ b/Documentation/driver-api/usb/writing_usb_driver.rst
@@ -218,36 +218,36 @@ do very much processing at that time. Our implementation of
 ``skel_write_bulk_callback`` merely reports if the urb was completed
 successfully or not and then returns.
 
-The read function works a bit differently from the write function in
+This read function works a bit differently from the write function in
 that we do not use an urb to transfer data from the device to the
-driver. Instead we call the :c:func:`usb_bulk_msg` function, which can be used
+driver. Instead we call usb_bulk_msg(), which can be used
 to send or receive data from a device without having to create urbs and
-handle urb completion callback functions. We call the :c:func:`usb_bulk_msg`
-function, giving it a buffer into which to place any data received from
+handle urb completion callback functions. We call usb_bulk_msg(),
+giving it a buffer into which to place any data received from
 the device and a timeout value. If the timeout period expires without
 receiving any data from the device, the function will fail and return an
 error message. This can be shown with the following code::
 
     /* do an immediate bulk read to get data from the device */
-    retval = usb_bulk_msg (skel->dev,
-			   usb_rcvbulkpipe (skel->dev,
-			   skel->bulk_in_endpointAddr),
-			   skel->bulk_in_buffer,
-			   skel->bulk_in_size,
-			   &count, 5000);
+    rv = usb_bulk_msg(dev->udev,
+		      usb_rcvbulkpipe (dev->udev,
+		      dev->bulk_in_endpointAddr),
+		      dev->bulk_in_buffer,
+	              dev->bulk_in_size,
+		      &len, 5000);
     /* if the read was successful, copy the data to user space */
-    if (!retval) {
-	    if (copy_to_user (buffer, skel->bulk_in_buffer, count))
-		    retval = -EFAULT;
+    if (!rv) {
+	    if (copy_to_user (buffer, dev->bulk_in_buffer, len))
+		    rv = -EFAULT;
 	    else
-		    retval = count;
+		    rv = len;
     }
 
 
-The :c:func:`usb_bulk_msg` function can be very useful for doing single reads
+usb_bulk_msg() can be very useful for doing single reads
 or writes to a device; however, if you need to read or write constantly to
 a device, it is recommended to set up your own urbs and submit them to
-the USB subsystem.
+the USB subsystem. The template uses urbs for read and write.
 
 When the user program releases the file handle that it has been using to
 talk to the device, the release function in the driver is called. In
-- 
2.25.1

Re: [PATCH v2 1/4] Docs: usb: update usb_bulk_msg receiving example

[Greg KH]

On Sat, Dec 04, 2021 at 05:35:11PM +0100, Philipp Hortmann wrote:
> Clarification that this example is not in the driver template anymore.
> Update code example so that it fits best to usb-skeleton.c
> Update format of function names
> 
> Signed-off-by: Philipp Hortmann <philipp.g.hortmann@gmail.com>
> ---
> V1 -> V2: Added "Update format of function names" to patch description
>           Corrected format of function names like the following example:
>           "`usb_bulk_msg` function" to "usb_bulk_msg()"
> ---
>  .../driver-api/usb/writing_usb_driver.rst     | 32 +++++++++----------
>  1 file changed, 16 insertions(+), 16 deletions(-)
> 
> diff --git a/Documentation/driver-api/usb/writing_usb_driver.rst b/Documentation/driver-api/usb/writing_usb_driver.rst
> index b43e1ce49f0e..ed11398837e5 100644
> --- a/Documentation/driver-api/usb/writing_usb_driver.rst
> +++ b/Documentation/driver-api/usb/writing_usb_driver.rst
> @@ -218,36 +218,36 @@ do very much processing at that time. Our implementation of
>  ``skel_write_bulk_callback`` merely reports if the urb was completed
>  successfully or not and then returns.
>  
> -The read function works a bit differently from the write function in
> +This read function works a bit differently from the write function in
>  that we do not use an urb to transfer data from the device to the
> -driver. Instead we call the :c:func:`usb_bulk_msg` function, which can be used
> +driver. Instead we call usb_bulk_msg(), which can be used
>  to send or receive data from a device without having to create urbs and
> -handle urb completion callback functions. We call the :c:func:`usb_bulk_msg`
> -function, giving it a buffer into which to place any data received from
> +handle urb completion callback functions. We call usb_bulk_msg(),
> +giving it a buffer into which to place any data received from
>  the device and a timeout value. If the timeout period expires without
>  receiving any data from the device, the function will fail and return an
>  error message. This can be shown with the following code::
>  
>      /* do an immediate bulk read to get data from the device */
> -    retval = usb_bulk_msg (skel->dev,
> -			   usb_rcvbulkpipe (skel->dev,
> -			   skel->bulk_in_endpointAddr),
> -			   skel->bulk_in_buffer,
> -			   skel->bulk_in_size,
> -			   &count, 5000);
> +    rv = usb_bulk_msg(dev->udev,

Why are you changing the varible name?  That seems unnecessary.

> +		      usb_rcvbulkpipe (dev->udev,
> +		      dev->bulk_in_endpointAddr),
> +		      dev->bulk_in_buffer,
> +	              dev->bulk_in_size,
> +		      &len, 5000);
>      /* if the read was successful, copy the data to user space */
> -    if (!retval) {
> -	    if (copy_to_user (buffer, skel->bulk_in_buffer, count))
> -		    retval = -EFAULT;
> +    if (!rv) {
> +	    if (copy_to_user (buffer, dev->bulk_in_buffer, len))
> +		    rv = -EFAULT;
>  	    else
> -		    retval = count;
> +		    rv = len;
>      }

Leaving the variable name alone keeps this patch much smaller.

>  
>  
> -The :c:func:`usb_bulk_msg` function can be very useful for doing single reads
> +usb_bulk_msg() can be very useful for doing single reads

You are doing different things in this patch, one is converting the
function style and one is updating the text.  How about doing just the
function name stuff first, all in one patch, and then the updates, as
that would make it much easier to read.

Also, any reason you aren't cc:ing the USB maintainer on these changes?  :)

thanks,

greg k-h

Re: [PATCH v2 1/4] Docs: usb: update usb_bulk_msg receiving example

[Philipp Hortmann]

On 12/5/21 12:00 PM, Greg KH wrote:
> On Sat, Dec 04, 2021 at 05:35:11PM +0100, Philipp Hortmann wrote:
>> Clarification that this example is not in the driver template anymore.
>> Update code example so that it fits best to usb-skeleton.c
>> Update format of function names
>>
>> Signed-off-by: Philipp Hortmann <philipp.g.hortmann@gmail.com>
>> ---
>> V1 -> V2: Added "Update format of function names" to patch description
>>            Corrected format of function names like the following example:
>>            "`usb_bulk_msg` function" to "usb_bulk_msg()"
>> ---
>>   .../driver-api/usb/writing_usb_driver.rst     | 32 +++++++++----------
>>   1 file changed, 16 insertions(+), 16 deletions(-)
>>
>> diff --git a/Documentation/driver-api/usb/writing_usb_driver.rst b/Documentation/driver-api/usb/writing_usb_driver.rst
>> index b43e1ce49f0e..ed11398837e5 100644
>> --- a/Documentation/driver-api/usb/writing_usb_driver.rst
>> +++ b/Documentation/driver-api/usb/writing_usb_driver.rst
>> @@ -218,36 +218,36 @@ do very much processing at that time. Our implementation of
>>   ``skel_write_bulk_callback`` merely reports if the urb was completed
>>   successfully or not and then returns.
>>   
>> -The read function works a bit differently from the write function in
>> +This read function works a bit differently from the write function in
>>   that we do not use an urb to transfer data from the device to the
>> -driver. Instead we call the :c:func:`usb_bulk_msg` function, which can be used
>> +driver. Instead we call usb_bulk_msg(), which can be used
>>   to send or receive data from a device without having to create urbs and
>> -handle urb completion callback functions. We call the :c:func:`usb_bulk_msg`
>> -function, giving it a buffer into which to place any data received from
>> +handle urb completion callback functions. We call usb_bulk_msg(),
>> +giving it a buffer into which to place any data received from
>>   the device and a timeout value. If the timeout period expires without
>>   receiving any data from the device, the function will fail and return an
>>   error message. This can be shown with the following code::
>>   
>>       /* do an immediate bulk read to get data from the device */
>> -    retval = usb_bulk_msg (skel->dev,
>> -			   usb_rcvbulkpipe (skel->dev,
>> -			   skel->bulk_in_endpointAddr),
>> -			   skel->bulk_in_buffer,
>> -			   skel->bulk_in_size,
>> -			   &count, 5000);
>> +    rv = usb_bulk_msg(dev->udev,
> 
> Why are you changing the varible name?  That seems unnecessary.
Reason is that retval does not exist in skel_read().
> 
>> +		      usb_rcvbulkpipe (dev->udev,
>> +		      dev->bulk_in_endpointAddr),
>> +		      dev->bulk_in_buffer,
>> +	              dev->bulk_in_size,
>> +		      &len, 5000);
>>       /* if the read was successful, copy the data to user space */
>> -    if (!retval) {
>> -	    if (copy_to_user (buffer, skel->bulk_in_buffer, count))
>> -		    retval = -EFAULT;
>> +    if (!rv) {
>> +	    if (copy_to_user (buffer, dev->bulk_in_buffer, len))
>> +		    rv = -EFAULT;
>>   	    else
>> -		    retval = count;
>> +		    rv = len;
>>       }
> 
> Leaving the variable name alone keeps this patch much smaller.
Will leave the variable name in the next patch.
> 
>>   
>>   
>> -The :c:func:`usb_bulk_msg` function can be very useful for doing single reads
>> +usb_bulk_msg() can be very useful for doing single reads
> 
> You are doing different things in this patch, one is converting the
> function style and one is updating the text.  How about doing just the
> function name stuff first, all in one patch, and then the updates, as
> that would make it much easier to read.
Will be changed.
> 
> Also, any reason you aren't cc:ing the USB maintainer on these changes?  :)
According to:
perl scripts/get_maintainer.pl --separator , --nokeywords --nogit 
--nogit-fallback --norolestats -f 
Documentation/driver-api/usb/writing_usb_driver.rst
Jonathan Corbet 
<corbet@lwn.net>,linux-doc@vger.kernel.org,linux-kernel@vger.kernel.org
you are not in charge.
thanks,
Philipp Hortmann
> thanks,
> 
> greg k-h
> 

Re: [PATCH v2 1/4] Docs: usb: update usb_bulk_msg receiving example

[Greg KH]

On Sun, Dec 05, 2021 at 06:04:48PM +0100, Philipp Hortmann wrote:
> On 12/5/21 12:00 PM, Greg KH wrote:
> > On Sat, Dec 04, 2021 at 05:35:11PM +0100, Philipp Hortmann wrote:
> > > Clarification that this example is not in the driver template anymore.
> > > Update code example so that it fits best to usb-skeleton.c
> > > Update format of function names
> > > 
> > > Signed-off-by: Philipp Hortmann <philipp.g.hortmann@gmail.com>
> > > ---
> > > V1 -> V2: Added "Update format of function names" to patch description
> > >            Corrected format of function names like the following example:
> > >            "`usb_bulk_msg` function" to "usb_bulk_msg()"
> > > ---
> > >   .../driver-api/usb/writing_usb_driver.rst     | 32 +++++++++----------
> > >   1 file changed, 16 insertions(+), 16 deletions(-)
> > > 
> > > diff --git a/Documentation/driver-api/usb/writing_usb_driver.rst b/Documentation/driver-api/usb/writing_usb_driver.rst
> > > index b43e1ce49f0e..ed11398837e5 100644
> > > --- a/Documentation/driver-api/usb/writing_usb_driver.rst
> > > +++ b/Documentation/driver-api/usb/writing_usb_driver.rst
> > > @@ -218,36 +218,36 @@ do very much processing at that time. Our implementation of
> > >   ``skel_write_bulk_callback`` merely reports if the urb was completed
> > >   successfully or not and then returns.
> > > -The read function works a bit differently from the write function in
> > > +This read function works a bit differently from the write function in
> > >   that we do not use an urb to transfer data from the device to the
> > > -driver. Instead we call the :c:func:`usb_bulk_msg` function, which can be used
> > > +driver. Instead we call usb_bulk_msg(), which can be used
> > >   to send or receive data from a device without having to create urbs and
> > > -handle urb completion callback functions. We call the :c:func:`usb_bulk_msg`
> > > -function, giving it a buffer into which to place any data received from
> > > +handle urb completion callback functions. We call usb_bulk_msg(),
> > > +giving it a buffer into which to place any data received from
> > >   the device and a timeout value. If the timeout period expires without
> > >   receiving any data from the device, the function will fail and return an
> > >   error message. This can be shown with the following code::
> > >       /* do an immediate bulk read to get data from the device */
> > > -    retval = usb_bulk_msg (skel->dev,
> > > -			   usb_rcvbulkpipe (skel->dev,
> > > -			   skel->bulk_in_endpointAddr),
> > > -			   skel->bulk_in_buffer,
> > > -			   skel->bulk_in_size,
> > > -			   &count, 5000);
> > > +    rv = usb_bulk_msg(dev->udev,
> > 
> > Why are you changing the varible name?  That seems unnecessary.
> Reason is that retval does not exist in skel_read().

Neither does any call to usb_bulk_msg().  So this is not code that is
from that file at all.  "retval" is easier to understand than "rv".

> > Also, any reason you aren't cc:ing the USB maintainer on these changes?  :)
> According to:
> perl scripts/get_maintainer.pl --separator , --nokeywords --nogit
> --nogit-fallback --norolestats -f
> Documentation/driver-api/usb/writing_usb_driver.rst
> Jonathan Corbet
> <corbet@lwn.net>,linux-doc@vger.kernel.org,linux-kernel@vger.kernel.org
> you are not in charge.

Ah, documentation isn't added to the maintainers entry for USB, I'll go
fix that up...

But note, my name is at the top of that file still, right?

thanks,

greg k-h

[PATCH v2 2/4] Docs: usb: update comment and code near decrement our usage count for the device

[Philipp Hortmann]

Put release function in the document typical form
Update comment: decrement our usage count ..
and code according to usb-skeleton.c

Signed-off-by: Philipp Hortmann <philipp.g.hortmann@gmail.com>
---
V1 -> V2: Corrected format of function name to skel_release()
---
 Documentation/driver-api/usb/writing_usb_driver.rst | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/Documentation/driver-api/usb/writing_usb_driver.rst b/Documentation/driver-api/usb/writing_usb_driver.rst
index ed11398837e5..297b622f5438 100644
--- a/Documentation/driver-api/usb/writing_usb_driver.rst
+++ b/Documentation/driver-api/usb/writing_usb_driver.rst
@@ -250,12 +250,12 @@ a device, it is recommended to set up your own urbs and submit them to
 the USB subsystem. The template uses urbs for read and write.
 
 When the user program releases the file handle that it has been using to
-talk to the device, the release function in the driver is called. In
+talk to the device, skel_release() in the driver is called. In
 this function we decrement our private usage count and wait for possible
 pending writes::
 
-    /* decrement our usage count for the device */
-    --skel->open_count;
+    /* decrement the count on our device */
+    kref_put(&dev->kref, skel_delete);
 
 
 One of the more difficult problems that USB drivers must be able to
-- 
2.25.1

[PATCH v2 3/4] Docs: usb: update comment and code of function skel_delete

[Philipp Hortmann]

Put skel_delete function in the document typical form
Update code according to usb-skeleton.c

Signed-off-by: Philipp Hortmann <philipp.g.hortmann@gmail.com>
---
V1 -> V2: Corrected format of function name to skel_delete()
---
 .../driver-api/usb/writing_usb_driver.rst     | 21 +++++++++----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/Documentation/driver-api/usb/writing_usb_driver.rst b/Documentation/driver-api/usb/writing_usb_driver.rst
index 297b622f5438..b459f9e089e0 100644
--- a/Documentation/driver-api/usb/writing_usb_driver.rst
+++ b/Documentation/driver-api/usb/writing_usb_driver.rst
@@ -262,19 +262,18 @@ One of the more difficult problems that USB drivers must be able to
 handle smoothly is the fact that the USB device may be removed from the
 system at any point in time, even if a program is currently talking to
 it. It needs to be able to shut down any current reads and writes and
-notify the user-space programs that the device is no longer there. The
-following code (function ``skel_delete``) is an example of how to do
-this::
+notify the user-space programs that the device is no longer there.
+skel_delete() is an example of how to do this::
 
-    static inline void skel_delete (struct usb_skel *dev)
+    static void skel_delete(struct kref *kref)
     {
-	kfree (dev->bulk_in_buffer);
-	if (dev->bulk_out_buffer != NULL)
-	    usb_free_coherent (dev->udev, dev->bulk_out_size,
-		dev->bulk_out_buffer,
-		dev->write_urb->transfer_dma);
-	usb_free_urb (dev->write_urb);
-	kfree (dev);
+	struct usb_skel *dev = to_skel_dev(kref);
+
+	usb_free_urb(dev->bulk_in_urb);
+	usb_put_intf(dev->interface);
+	usb_put_dev(dev->udev);
+	kfree(dev->bulk_in_buffer);
+	kfree(dev);
     }
 
 
-- 
2.25.1

[PATCH v2 4/4] Docs: usb: update explanation for device_present to disconnected

[Philipp Hortmann]

Update text for `device_present` flag to `disconnected` flag

Signed-off-by: Philipp Hortmann <philipp.g.hortmann@gmail.com>
---
V1 -> V2: Corrected format of function name to skel_disconnect()
---
 .../driver-api/usb/writing_usb_driver.rst          | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/Documentation/driver-api/usb/writing_usb_driver.rst b/Documentation/driver-api/usb/writing_usb_driver.rst
index b459f9e089e0..fa795b8d7eac 100644
--- a/Documentation/driver-api/usb/writing_usb_driver.rst
+++ b/Documentation/driver-api/usb/writing_usb_driver.rst
@@ -277,15 +277,13 @@ skel_delete() is an example of how to do this::
     }
 
 
-If a program currently has an open handle to the device, we reset the
-flag ``device_present``. For every read, write, release and other
+If the driver probed the device successfully, the flag ``disconnected``
+is initialized and set to false. For every read, write and other
 functions that expect a device to be present, the driver first checks
-this flag to see if the device is still present. If not, it releases
-that the device has disappeared, and a ``-ENODEV`` error is returned to the
-user-space program. When the release function is eventually called, it
-determines if there is no device and if not, it does the cleanup that
-the ``skel_disconnect`` function normally does if there are no open files
-on the device (see Listing 5).
+this flag to see if the device is still present. If not, a ``-ENODEV``
+error is returned to the user-space program. When the device is
+disconnected, skel_disconnect() is called. It sets ``disconnected``
+to true and cleans up.
 
 Isochronous Data
 ================
-- 
2.25.1