serial device name for smart card reader that is integrated to Anysee DVB USB device

serial device name for smart card reader that is integrated to Anysee DVB USB device

[Antti Palosaari]

I have been looking for correct device name for serial smart card reader 
that is integrated to Anysee DVB USB devices. Consider it like old so 
called Phoenix reader. Phoenix is de facto protocol used for such 
readers and there is whole bunch of different RS232 (/dev/ttyS#) or 
USB-serial (/dev/ttyUSB#) readers using that protocol.

Anyhow, that one is integrated to DVB USB device that is driven by 
dvb_usb_anysee driver. As I understand, I need reserve new device name 
and major number for my device. See Documentation/devices.txt

Current proof-of-concept driver can be found from:
http://git.linuxtv.org/anttip/media_tree.git/shortlog/refs/heads/anysee-sc
Don't review code since it is not ready for release yet, it even lacks 
locking.

There have been some proposes about names, mainly whether to register it 
under the DVB adapter it is physically (/dev/dvb/adapterN/sc#) or to the 
root of /dev (/dev/sc#). I used sc as name, SC=SmartCard.

Could someone who have enough knowledge point out which one is correct 
or better?


regards
Antti

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Re: serial device name for smart card reader that is integrated to Anysee DVB USB device

[Greg KH]

On Wed, Oct 05, 2011 at 12:22:09AM +0300, Antti Palosaari wrote:
> I have been looking for correct device name for serial smart card
> reader that is integrated to Anysee DVB USB devices. Consider it
> like old so called Phoenix reader. Phoenix is de facto protocol used
> for such readers and there is whole bunch of different RS232
> (/dev/ttyS#) or USB-serial (/dev/ttyUSB#) readers using that
> protocol.
> 
> Anyhow, that one is integrated to DVB USB device that is driven by
> dvb_usb_anysee driver. As I understand, I need reserve new device
> name and major number for my device. See Documentation/devices.txt

Why not just use the usb-serial core and then you get a ttyUSB* device
node "for free"?  It also should provide a lot of the basic tty
infrastructure and ring buffer logic all ready to use.

thanks,

greg k-h



> 
> Current proof-of-concept driver can be found from:
> http://git.linuxtv.org/anttip/media_tree.git/shortlog/refs/heads/anysee-sc
> Don't review code since it is not ready for release yet, it even
> lacks locking.
> 
> There have been some proposes about names, mainly whether to
> register it under the DVB adapter it is physically
> (/dev/dvb/adapterN/sc#) or to the root of /dev (/dev/sc#). I used sc
> as name, SC=SmartCard.
> 
> Could someone who have enough knowledge point out which one is
> correct or better?
> 
> 
> regards
> Antti
> 
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> http://palosaari.fi/
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Re: serial device name for smart card reader that is integrated to Anysee DVB USB device

[Antti Palosaari]

On 10/05/2011 07:59 AM, Greg KH wrote:
> On Wed, Oct 05, 2011 at 12:22:09AM +0300, Antti Palosaari wrote:
>> I have been looking for correct device name for serial smart card
>> reader that is integrated to Anysee DVB USB devices. Consider it
>> like old so called Phoenix reader. Phoenix is de facto protocol used
>> for such readers and there is whole bunch of different RS232
>> (/dev/ttyS#) or USB-serial (/dev/ttyUSB#) readers using that
>> protocol.
>>
>> Anyhow, that one is integrated to DVB USB device that is driven by
>> dvb_usb_anysee driver. As I understand, I need reserve new device
>> name and major number for my device. See Documentation/devices.txt
>
> Why not just use the usb-serial core and then you get a ttyUSB* device
> node "for free"?  It also should provide a lot of the basic tty
> infrastructure and ring buffer logic all ready to use.

Since I don't see how I can access same platform data from DVB USB  and 
USB-serial driver (usb_set_intfdata). I asked that earlier, see: 
http://www.mail-archive.com/linux-media@vger.kernel.org/msg36027.html

regards
Antti

-- 
http://palosaari.fi/

Re: serial device name for smart card reader that is integrated to Anysee DVB USB device

[Oliver Neukum]

Am Mittwoch, 5. Oktober 2011, 07:58:51 schrieb Antti Palosaari:
> On 10/05/2011 07:59 AM, Greg KH wrote:

> > Why not just use the usb-serial core and then you get a ttyUSB* device
> > node "for free"?  It also should provide a lot of the basic tty
> > infrastructure and ring buffer logic all ready to use.
> 
> Since I don't see how I can access same platform data from DVB USB  and 
> USB-serial driver (usb_set_intfdata). I asked that earlier, see: 
> http://www.mail-archive.com/linux-media@vger.kernel.org/msg36027.html

Yes, and I'll have to give you the same answer as then.

But, Greg, Antti makes a very valid point here. The generic code assumes that
it owns intfdata, that is you cannot use it as is for access to anything that lacks
its own interface. But this is not a fatal flaw. We can alter the generic code to use
an accessor function the driver can provide and make it default to get/set_intfdata

What do you think?

	Regards
		Oliver
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Re: serial device name for smart card reader that is integrated to Anysee DVB USB device

[Antti Palosaari]

On 10/05/2011 09:15 AM, Oliver Neukum wrote:
> Am Mittwoch, 5. Oktober 2011, 07:58:51 schrieb Antti Palosaari:
>> On 10/05/2011 07:59 AM, Greg KH wrote:
>
>>> Why not just use the usb-serial core and then you get a ttyUSB* device
>>> node "for free"?  It also should provide a lot of the basic tty
>>> infrastructure and ring buffer logic all ready to use.
>>
>> Since I don't see how I can access same platform data from DVB USB  and
>> USB-serial driver (usb_set_intfdata). I asked that earlier, see:
>> http://www.mail-archive.com/linux-media@vger.kernel.org/msg36027.html
>
> Yes, and I'll have to give you the same answer as then.
>
> But, Greg, Antti makes a very valid point here. The generic code assumes that
> it owns intfdata, that is you cannot use it as is for access to anything that lacks
> its own interface. But this is not a fatal flaw. We can alter the generic code to use
> an accessor function the driver can provide and make it default to get/set_intfdata
>
> What do you think?

Oliver, I looked your old thread reply but I didn't catch how you meant 
it to happen. Could you give some small example?

regards
Antti

-- 
http://palosaari.fi/

Re: serial device name for smart card reader that is integrated to Anysee DVB USB device

[Oliver Neukum]

Am Mittwoch, 5. Oktober 2011, 08:19:10 schrieb Antti Palosaari:
> On 10/05/2011 09:15 AM, Oliver Neukum wrote:

> > But, Greg, Antti makes a very valid point here. The generic code assumes that
> > it owns intfdata, that is you cannot use it as is for access to anything that lacks
> > its own interface. But this is not a fatal flaw. We can alter the generic code to use
> > an accessor function the driver can provide and make it default to get/set_intfdata
> >
> > What do you think?
> 
> Oliver, I looked your old thread reply but I didn't catch how you meant 
> it to happen. Could you give some small example?

Look at this structure:

struct dvb_usb_device {
        struct dvb_usb_device_properties props;
        struct dvb_usb_device_description *desc;

        struct usb_device *udev;

#define DVB_USB_STATE_INIT        0x000
#define DVB_USB_STATE_I2C         0x001
#define DVB_USB_STATE_DVB         0x002
#define DVB_USB_STATE_REMOTE      0x004
        int state;

        int powered;

        /* locking */
        struct mutex usb_mutex;

        /* i2c */
        struct mutex i2c_mutex;
        struct i2c_adapter i2c_adap;

        int                    num_adapters_initialized;
        struct dvb_usb_adapter adapter[MAX_NO_OF_ADAPTER_PER_DEVICE];

        /* remote control */
        struct rc_dev *rc_dev;
        struct input_dev *input_dev;
        char rc_phys[64];
        struct delayed_work rc_query_work;
        u32 last_event;
        int last_state;

        struct module *owner;

        void *priv;
};

It contains a pointer to an input device. You could add a pointer to a usb
serial device here. This leaves you with two problems.

1. The USB serial layer will try to set intfdata

We will need to change it to use a function the driver provides to store
a pointer to its private data.

2. The usb serial layer will not learn about events it needs to learn about.

We need to extended the usb dvb code to call into a sufficiently abstracted
method in the usb serial code.


Conceptually the usb serial code is ready to share an interface among
multiple serial ports, but not to share an interface with something else.
I described the steps necesary to allow that. This is new, so there are
no examples.

	Regards
		Oliver

Re: serial device name for smart card reader that is integrated to Anysee DVB USB device

[Oliver Neukum]

Am Mittwoch, 5. Oktober 2011, 10:16:06 schrieb Oliver Neukum:
> Am Mittwoch, 5. Oktober 2011, 08:19:10 schrieb Antti Palosaari:
> > On 10/05/2011 09:15 AM, Oliver Neukum wrote:
> 
> > > But, Greg, Antti makes a very valid point here. The generic code assumes that
> > > it owns intfdata, that is you cannot use it as is for access to anything that lacks
> > > its own interface. But this is not a fatal flaw. We can alter the generic code to use
> > > an accessor function the driver can provide and make it default to get/set_intfdata
> > >
> > > What do you think?
> > 
> > Oliver, I looked your old thread reply but I didn't catch how you meant 
> > it to happen. Could you give some small example?

Hi,

here is the code I come up with at an early, extremely incomplete stage.
Just for your information because I'll stop working on this for a few days.

	Regards
		Oliver

diff --git a/drivers/media/dvb/dvb-usb/anysee.c b/drivers/media/dvb/dvb-usb/anysee.c
index 2cbf19a..34c950a 100644
--- a/drivers/media/dvb/dvb-usb/anysee.c
+++ b/drivers/media/dvb/dvb-usb/anysee.c
@@ -31,6 +31,12 @@
  * is highly welcome!
  */
 
+#include <linux/kernel.h>
+#include <linux/tty_driver.h>
+#include <linux/tty.h>
+#include <linux/serial.h>
+#include <linux/usb.h>
+#include <linux/usb/serial.h>
 #include "anysee.h"
 #include "tda1002x.h"
 #include "mt352.h"
@@ -898,6 +904,8 @@ static int anysee_probe(struct usb_interface *intf,
 	if (ret)
 		return ret;
 
+	usb_serial_start(d->card_dev, intf);
+
 	return anysee_init(d);
 }
 
@@ -973,6 +981,10 @@ static int __init anysee_module_init(void)
 	if (ret)
 		err("%s: usb_register failed. Error number %d", __func__, ret);
 
+	ret = usb_serial_register(&anysee_card_driver);
+	if (ret)
+		usb_deregister(&anysee_driver);
+
 	return ret;
 }
 
diff --git a/drivers/media/dvb/dvb-usb/anysee.h b/drivers/media/dvb/dvb-usb/anysee.h
index ad6ccd1..f1ca088 100644
--- a/drivers/media/dvb/dvb-usb/anysee.h
+++ b/drivers/media/dvb/dvb-usb/anysee.h
@@ -61,6 +61,9 @@ struct anysee_state {
 	u8 seq;
 };
 
+static struct usb_serial_driver anysee_card_driver = {
+};
+
 #define ANYSEE_HW_507T    2 /* E30 */
 #define ANYSEE_HW_507CD   6 /* E30 Plus */
 #define ANYSEE_HW_507DC  10 /* E30 C Plus */
diff --git a/drivers/media/dvb/dvb-usb/dvb-usb.h b/drivers/media/dvb/dvb-usb/dvb-usb.h
index 7d35d07..5333c4d 100644
--- a/drivers/media/dvb/dvb-usb/dvb-usb.h
+++ b/drivers/media/dvb/dvb-usb/dvb-usb.h
@@ -425,6 +425,7 @@ struct dvb_usb_device {
 	/* remote control */
 	struct rc_dev *rc_dev;
 	struct input_dev *input_dev;
+	struct usb_serial *card_dev;
 	char rc_phys[64];
 	struct delayed_work rc_query_work;
 	u32 last_event;
diff --git a/drivers/usb/serial/generic.c b/drivers/usb/serial/generic.c
index e4db5ad..4c387ab 100644
--- a/drivers/usb/serial/generic.c
+++ b/drivers/usb/serial/generic.c
@@ -175,6 +175,12 @@ int usb_serial_generic_prepare_write_buffer(struct usb_serial_port *port,
 	return kfifo_out_locked(&port->write_fifo, dest, size, &port->lock);
 }
 
+void usb_serial_generic_set_private_data(struct usb_interface *intf, struct usb_serial *serial)
+{
+	usb_set_intfdata(intf, serial);
+}
+EXPORT_SYMBOL_GPL(usb_serial_generic_set_private_data);
+
 /**
  * usb_serial_generic_write_start - kick off an URB write
  * @port:	Pointer to the &struct usb_serial_port data
diff --git a/drivers/usb/serial/usb-serial.c b/drivers/usb/serial/usb-serial.c
index 1c03130..dd8cf75 100644
--- a/drivers/usb/serial/usb-serial.c
+++ b/drivers/usb/serial/usb-serial.c
@@ -707,19 +707,18 @@ static const struct tty_port_operations serial_port_ops = {
 	.shutdown = serial_down,
 };
 
-int usb_serial_probe(struct usb_interface *interface,
-			       const struct usb_device_id *id)
+int usb_serial_start(struct usb_serial *serial, struct usb_interface *interface)
 {
 	struct usb_device *dev = interface_to_usbdev(interface);
-	struct usb_serial *serial = NULL;
-	struct usb_serial_port *port;
+	struct usb_serial_driver *type = NULL;
 	struct usb_host_interface *iface_desc;
 	struct usb_endpoint_descriptor *endpoint;
 	struct usb_endpoint_descriptor *interrupt_in_endpoint[MAX_NUM_PORTS];
 	struct usb_endpoint_descriptor *interrupt_out_endpoint[MAX_NUM_PORTS];
 	struct usb_endpoint_descriptor *bulk_in_endpoint[MAX_NUM_PORTS];
 	struct usb_endpoint_descriptor *bulk_out_endpoint[MAX_NUM_PORTS];
-	struct usb_serial_driver *type = NULL;
+	struct usb_serial_port *port;
+
 	int retval;
 	unsigned int minor;
 	int buffer_size;
@@ -731,28 +730,6 @@ int usb_serial_probe(struct usb_interface *interface,
 	int num_ports = 0;
 	int max_endpoints;
 
-	mutex_lock(&table_lock);
-	type = search_serial_device(interface);
-	if (!type) {
-		mutex_unlock(&table_lock);
-		dbg("none matched");
-		return -ENODEV;
-	}
-
-	if (!try_module_get(type->driver.owner)) {
-		mutex_unlock(&table_lock);
-		dev_err(&interface->dev, "module get failed, exiting\n");
-		return -EIO;
-	}
-	mutex_unlock(&table_lock);
-
-	serial = create_serial(dev, interface, type);
-	if (!serial) {
-		module_put(type->driver.owner);
-		dev_err(&interface->dev, "%s - out of memory\n", __func__);
-		return -ENOMEM;
-	}
-
 	/* if this device type has a probe function, call it */
 	if (type->probe) {
 		const struct usb_device_id *id;
@@ -1087,7 +1064,8 @@ int usb_serial_probe(struct usb_interface *interface,
 
 exit:
 	/* success */
-	usb_set_intfdata(interface, serial);
+	serial->type->set_private_data(interface, serial);
+	//usb_set_intfdata(interface, serial);
 	module_put(type->driver.owner);
 	return 0;
 
@@ -1096,6 +1074,39 @@ probe_error:
 	module_put(type->driver.owner);
 	return -EIO;
 }
+EXPORT_SYMBOL_GPL(usb_serial_start);
+
+int usb_serial_probe(struct usb_interface *interface,
+			       const struct usb_device_id *id)
+{
+	struct usb_device *dev = interface_to_usbdev(interface);
+	struct usb_serial *serial = NULL;
+	struct usb_serial_driver *type = NULL;
+
+	mutex_lock(&table_lock);
+	type = search_serial_device(interface);
+	if (!type) {
+		mutex_unlock(&table_lock);
+		dbg("none matched");
+		return -ENODEV;
+	}
+
+	if (!try_module_get(type->driver.owner)) {
+		mutex_unlock(&table_lock);
+		dev_err(&interface->dev, "module get failed, exiting\n");
+		return -EIO;
+	}
+	mutex_unlock(&table_lock);
+
+	serial = create_serial(dev, interface, type);
+	if (!serial) {
+		module_put(type->driver.owner);
+		dev_err(&interface->dev, "%s - out of memory\n", __func__);
+		return -ENOMEM;
+	}
+
+	return usb_serial_start(serial, interface);
+}
 EXPORT_SYMBOL_GPL(usb_serial_probe);
 
 void usb_serial_disconnect(struct usb_interface *interface)
@@ -1109,7 +1120,8 @@ void usb_serial_disconnect(struct usb_interface *interface)
 	dbg("%s", __func__);
 
 	mutex_lock(&serial->disc_mutex);
-	usb_set_intfdata(interface, NULL);
+	serial->type->set_private_data(interface, NULL);
+
 	/* must set a flag, to signal subdrivers */
 	serial->disconnected = 1;
 	mutex_unlock(&serial->disc_mutex);
@@ -1148,11 +1160,11 @@ void usb_serial_disconnect(struct usb_interface *interface)
 	usb_serial_put(serial);
 	dev_info(dev, "device disconnected\n");
 }
+
 EXPORT_SYMBOL_GPL(usb_serial_disconnect);
 
-int usb_serial_suspend(struct usb_interface *intf, pm_message_t message)
+int usb_serial_do_suspend(struct usb_serial *serial, pm_message_t message)
 {
-	struct usb_serial *serial = usb_get_intfdata(intf);
 	struct usb_serial_port *port;
 	int i, r = 0;
 
@@ -1175,11 +1187,18 @@ int usb_serial_suspend(struct usb_interface *intf, pm_message_t message)
 err_out:
 	return r;
 }
-EXPORT_SYMBOL(usb_serial_suspend);
 
-int usb_serial_resume(struct usb_interface *intf)
+EXPORT_SYMBOL(usb_serial_do_suspend);
+
+int usb_serial_suspend(struct usb_interface *intf, pm_message_t message)
 {
 	struct usb_serial *serial = usb_get_intfdata(intf);
+	return usb_serial_do_suspend(serial, message);
+}
+EXPORT_SYMBOL(usb_serial_suspend);
+
+int usb_serial_do_resume(struct usb_serial *serial)
+{
 	int rv;
 
 	serial->suspending = 0;
@@ -1190,8 +1209,17 @@ int usb_serial_resume(struct usb_interface *intf)
 
 	return rv;
 }
+EXPORT_SYMBOL(usb_serial_do_resume);
+
+int usb_serial_resume(struct usb_interface *intf)
+{
+	struct usb_serial *serial = usb_get_intfdata(intf);
+	return usb_serial_do_resume(serial);
+}
+
 EXPORT_SYMBOL(usb_serial_resume);
 
+
 static const struct tty_operations serial_ops = {
 	.open =			serial_open,
 	.close =		serial_close,
@@ -1332,6 +1360,7 @@ static void fixup_generic(struct usb_serial_driver *device)
 	set_to_generic_if_null(device, release);
 	set_to_generic_if_null(device, process_read_urb);
 	set_to_generic_if_null(device, prepare_write_buffer);
+	set_to_generic_if_null(device, set_private_data);
 }
 
 int usb_serial_register(struct usb_serial_driver *driver)
diff --git a/include/linux/usb/serial.h b/include/linux/usb/serial.h
index b29f70b..396de61 100644
--- a/include/linux/usb/serial.h
+++ b/include/linux/usb/serial.h
@@ -243,6 +243,7 @@ struct usb_serial_driver {
 	int (*probe)(struct usb_serial *serial, const struct usb_device_id *id);
 	int (*attach)(struct usb_serial *serial);
 	int (*calc_num_ports) (struct usb_serial *serial);
+	void (*set_private_data) (struct usb_interface *intf, struct usb_serial *serial);
 
 	void (*disconnect)(struct usb_serial *serial);
 	void (*release)(struct usb_serial *serial);
@@ -301,10 +302,13 @@ extern void usb_serial_port_softint(struct usb_serial_port *port);
 
 extern int usb_serial_probe(struct usb_interface *iface,
 			    const struct usb_device_id *id);
+extern int usb_serial_start(struct usb_serial *serial, struct usb_interface *iface);
 extern void usb_serial_disconnect(struct usb_interface *iface);
 
 extern int usb_serial_suspend(struct usb_interface *intf, pm_message_t message);
+extern int usb_serial_do_suspend(struct usb_serial *serial, pm_message_t message); 
 extern int usb_serial_resume(struct usb_interface *intf);
+extern int usb_serial_do_resume(struct usb_serial *serial);
 
 extern int ezusb_writememory(struct usb_serial *serial, int address,
 			     unsigned char *data, int length, __u8 bRequest);
@@ -329,6 +333,7 @@ extern int usb_serial_generic_open(struct tty_struct *tty,
 extern int usb_serial_generic_write(struct tty_struct *tty,
 	struct usb_serial_port *port, const unsigned char *buf, int count);
 extern void usb_serial_generic_close(struct usb_serial_port *port);
+extern void usb_serial_generic_set_private_data(struct usb_interface *intf, struct usb_serial *serial);
 extern int usb_serial_generic_resume(struct usb_serial *serial);
 extern int usb_serial_generic_write_room(struct tty_struct *tty);
 extern int usb_serial_generic_chars_in_buffer(struct tty_struct *tty);
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Re: serial device name for smart card reader that is integrated to Anysee DVB USB device

[Antti Palosaari]

On 10/14/2011 08:32 PM, Oliver Neukum wrote:
> Am Mittwoch, 5. Oktober 2011, 10:16:06 schrieb Oliver Neukum:
>> Am Mittwoch, 5. Oktober 2011, 08:19:10 schrieb Antti Palosaari:
>>> On 10/05/2011 09:15 AM, Oliver Neukum wrote:
>>
>>>> But, Greg, Antti makes a very valid point here. The generic code assumes that
>>>> it owns intfdata, that is you cannot use it as is for access to anything that lacks
>>>> its own interface. But this is not a fatal flaw. We can alter the generic code to use
>>>> an accessor function the driver can provide and make it default to get/set_intfdata
>>>>
>>>> What do you think?
>>>
>>> Oliver, I looked your old thread reply but I didn't catch how you meant
>>> it to happen. Could you give some small example?
>
> here is the code I come up with at an early, extremely incomplete stage.
> Just for your information because I'll stop working on this for a few days.

I am back with that issue again. I just analysed both Oliver's code and 
usb-serial.c.

Problem are only these functions:
extern int usb_serial_probe(struct usb_interface *iface, const struct 
usb_device_id *id);
extern void usb_serial_disconnect(struct usb_interface *iface);
extern int usb_serial_suspend(struct usb_interface *intf, pm_message_t 
message);
extern int usb_serial_resume(struct usb_interface *intf);

as all those takes struct usb_interface as parameter. For the 
disconnect, suspend and resume it usb_interface param is used just for 
getting pointer to struct usb_serial. That's easy. The probe is more 
complex and needs some deeper changes. Main problem for probe seems to 
be also it saves struct usb_serial pointer to struct usb_interface 
usb_set_intfdata(interface, serial);

Anyhow, I would like now ask how to proceed. Should I export four new 
functions as replacement of those leaving old functionality as 
currently. Or should I change existing ones like adding new pointer for 
struct usb_serial and use it instead of struct usb_interface when not NULL.


regards
Antti

-- 
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Re: serial device name for smart card reader that is integrated to Anysee DVB USB device

[Alan Cox]

> Anyhow, I would like now ask how to proceed. Should I export four new 
> functions as replacement of those leaving old functionality as 
> currently. Or should I change existing ones like adding new pointer for 
> struct usb_serial and use it instead of struct usb_interface when not NULL.

I think I would favour adding new ones. The new ones can be added,
debugged and then the old ones phased out afterwards if it is worth
cleaning them up. That saves having to fix everything else at the same
time.

Alan

Re: serial device name for smart card reader that is integrated to Anysee DVB USB device

[Greg KH]

On Wed, Oct 05, 2011 at 08:15:17AM +0200, Oliver Neukum wrote:
> Am Mittwoch, 5. Oktober 2011, 07:58:51 schrieb Antti Palosaari:
> > On 10/05/2011 07:59 AM, Greg KH wrote:
> 
> > > Why not just use the usb-serial core and then you get a ttyUSB* device
> > > node "for free"?  It also should provide a lot of the basic tty
> > > infrastructure and ring buffer logic all ready to use.
> > 
> > Since I don't see how I can access same platform data from DVB USB  and 
> > USB-serial driver (usb_set_intfdata). I asked that earlier, see: 
> > http://www.mail-archive.com/linux-media@vger.kernel.org/msg36027.html
> 
> Yes, and I'll have to give you the same answer as then.
> 
> But, Greg, Antti makes a very valid point here. The generic code assumes that
> it owns intfdata, that is you cannot use it as is for access to anything that lacks
> its own interface. But this is not a fatal flaw. We can alter the generic code to use
> an accessor function the driver can provide and make it default to get/set_intfdata
> 
> What do you think?

I totally forgot about that previous answer, I write too much email :)

Anyway, yes, if we can alter the core to make this work for this type of
device, that is probably much easier than having to write a whole tty
driver just for this one type of device.  I'll gladly take such a patch.

thanks,

greg k-h