| Message ID | 20170903215404.425af4aa@vento.lan (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
2017-09-04 2:54 GMT+02:00 Mauro Carvalho Chehab <mchehab@s-opensource.com>: > Em Sun, 3 Sep 2017 22:05:23 +0200 > Honza Petrouš <jpetrous@gmail.com> escreveu: > >> 1) #define CA_SET_DESCR _IOW('o', 134, ca_descr_t) >> ============================================ >> >> CA_SET_DESCR is used for feeding descrambler device >> with correct keys (called here "control words") what >> allows to get services unscrambled. >> >> The best docu is: >> >> "Digital Video Broadcasting (DVB); >> Support for use of the DVB Scrambling Algorithm version 3 >> within digital broadcasting systems" >> >> Defined as DVB Document A125 and publicly >> available here: >> >> https://www.dvb.org/resources/public/standards/a125_dvb-csa3.pdf >> >> >> typedef struct ca_descr { >> unsigned int index; >> unsigned int parity; /* 0 == even, 1 == odd */ >> unsigned char cw[8]; >> } ca_descr_t; >> >> The 'index' is adress of the descrambler instance, as there exist >> limited number of them (retieved by CA_GET_DESCR_INFO). > > Thanks for the info. If I understood well, the enclosed patch should > be documenting it. > > > Thanks, > Mauro > > [PATCH] media: ca docs: document CA_SET_DESCR ioctl and structs > > The av7110 driver uses CA_SET_DESCR to store the descrambler > control words at the CA descrambler slots. > > Document it. > > Thanks-to: Honza Petrouš <jpetrous@gmail.com> > Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com> > > diff --git a/Documentation/media/uapi/dvb/ca-set-descr.rst b/Documentation/media/uapi/dvb/ca-set-descr.rst > index 9c484317d55c..a6c47205ffd8 100644 > --- a/Documentation/media/uapi/dvb/ca-set-descr.rst > +++ b/Documentation/media/uapi/dvb/ca-set-descr.rst > @@ -28,22 +28,11 @@ Arguments > ``msg`` > Pointer to struct :c:type:`ca_descr`. > > -.. c:type:: ca_descr > - > -.. code-block:: c > - > - struct ca_descr { > - unsigned int index; > - unsigned int parity; > - unsigned char cw[8]; > - }; > - > - > Description > ----------- > > -.. note:: This ioctl is undocumented. Documentation is welcome. > - > +CA_SET_DESCR is used for feeding descrambler CA slots with descrambling > +keys (refered as control words). > > Return Value > ------------ > diff --git a/include/uapi/linux/dvb/ca.h b/include/uapi/linux/dvb/ca.h > index f66ed53f4dc7..a62ddf0cebcd 100644 > --- a/include/uapi/linux/dvb/ca.h > +++ b/include/uapi/linux/dvb/ca.h > @@ -109,9 +109,16 @@ struct ca_msg { > unsigned char msg[256]; > }; > > +/** > + * struct ca_descr - CA descrambler control words info > + * > + * @index: CA Descrambler slot > + * @parity: control words parity, where 0 means even and 1 means odd > + * @cw: CA Descrambler control words > + */ > struct ca_descr { > unsigned int index; > - unsigned int parity; /* 0 == even, 1 == odd */ > + unsigned int parity; > unsigned char cw[8]; > }; > > Yeh, it should be that way. BTW, the only issue I have in mind is how to link particular descrambler with the PID after your removal of the CA_SET_PID. And yes, I know that currently we have no any user of such ioctl in our driver base :) /Honza
Em Mon, 4 Sep 2017 09:12:49 +0200 Honza Petrouš <jpetrous@gmail.com> escreveu: > 2017-09-04 2:54 GMT+02:00 Mauro Carvalho Chehab <mchehab@s-opensource.com>: > > Em Sun, 3 Sep 2017 22:05:23 +0200 > > Honza Petrouš <jpetrous@gmail.com> escreveu: > > > >> 1) #define CA_SET_DESCR _IOW('o', 134, ca_descr_t) > >> ============================================ > >> > >> CA_SET_DESCR is used for feeding descrambler device > >> with correct keys (called here "control words") what > >> allows to get services unscrambled. > >> > >> The best docu is: > >> > >> "Digital Video Broadcasting (DVB); > >> Support for use of the DVB Scrambling Algorithm version 3 > >> within digital broadcasting systems" > >> > >> Defined as DVB Document A125 and publicly > >> available here: > >> > >> https://www.dvb.org/resources/public/standards/a125_dvb-csa3.pdf > >> > >> > >> typedef struct ca_descr { > >> unsigned int index; > >> unsigned int parity; /* 0 == even, 1 == odd */ > >> unsigned char cw[8]; > >> } ca_descr_t; > >> > >> The 'index' is adress of the descrambler instance, as there exist > >> limited number of them (retieved by CA_GET_DESCR_INFO). > > > > Thanks for the info. If I understood well, the enclosed patch should > > be documenting it. > > > > > > Thanks, > > Mauro > > > > [PATCH] media: ca docs: document CA_SET_DESCR ioctl and structs > > > > The av7110 driver uses CA_SET_DESCR to store the descrambler > > control words at the CA descrambler slots. > > > > Document it. > > > > Thanks-to: Honza Petrouš <jpetrous@gmail.com> > > Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com> > > > > diff --git a/Documentation/media/uapi/dvb/ca-set-descr.rst b/Documentation/media/uapi/dvb/ca-set-descr.rst > > index 9c484317d55c..a6c47205ffd8 100644 > > --- a/Documentation/media/uapi/dvb/ca-set-descr.rst > > +++ b/Documentation/media/uapi/dvb/ca-set-descr.rst > > @@ -28,22 +28,11 @@ Arguments > > ``msg`` > > Pointer to struct :c:type:`ca_descr`. > > > > -.. c:type:: ca_descr > > - > > -.. code-block:: c > > - > > - struct ca_descr { > > - unsigned int index; > > - unsigned int parity; > > - unsigned char cw[8]; > > - }; > > - > > - > > Description > > ----------- > > > > -.. note:: This ioctl is undocumented. Documentation is welcome. > > - > > +CA_SET_DESCR is used for feeding descrambler CA slots with descrambling > > +keys (refered as control words). > > > > Return Value > > ------------ > > diff --git a/include/uapi/linux/dvb/ca.h b/include/uapi/linux/dvb/ca.h > > index f66ed53f4dc7..a62ddf0cebcd 100644 > > --- a/include/uapi/linux/dvb/ca.h > > +++ b/include/uapi/linux/dvb/ca.h > > @@ -109,9 +109,16 @@ struct ca_msg { > > unsigned char msg[256]; > > }; > > > > +/** > > + * struct ca_descr - CA descrambler control words info > > + * > > + * @index: CA Descrambler slot > > + * @parity: control words parity, where 0 means even and 1 means odd > > + * @cw: CA Descrambler control words > > + */ > > struct ca_descr { > > unsigned int index; > > - unsigned int parity; /* 0 == even, 1 == odd */ > > + unsigned int parity; > > unsigned char cw[8]; > > }; > > > > > > Yeh, it should be that way. Good! I'll add this patch to the series. > BTW, the only issue I have in mind is how to link particular > descrambler with the PID > after your removal of the CA_SET_PID. And yes, I know that currently we have > no any user of such ioctl in our driver base :) Well, I don't think that an ioctl like CA_SET_PID would solve it. On a generic case with is quite common nowadays on embedded hardware, We have K demods and M CIs (where K may be different than M). Also, You may need to route N PIDs to O descramblers. As user switch channels, the N PIDs should be unset, and another set of N' pids will be routed. CA_SET_PID allows to set just one PID, without identifying from what demod it would be received, and doesn't have a "reset" function to undo. So, IMHO, the interface is broken by design. Perhaps that's the reason why no upstream driver uses it. What seems to be a much better design would be to use the demux set filter ioctls and route the PIDs to the right CA. Thanks, Mauro
2017-09-04 11:06 GMT+02:00 Mauro Carvalho Chehab <mchehab@s-opensource.com>: > Em Mon, 4 Sep 2017 09:12:49 +0200 > Honza Petrouš <jpetrous@gmail.com> escreveu: > >> 2017-09-04 2:54 GMT+02:00 Mauro Carvalho Chehab <mchehab@s-opensource.com>: >> > Em Sun, 3 Sep 2017 22:05:23 +0200 >> > Honza Petrouš <jpetrous@gmail.com> escreveu: >> > >> >> 1) #define CA_SET_DESCR _IOW('o', 134, ca_descr_t) >> >> ============================================ >> >> >> >> CA_SET_DESCR is used for feeding descrambler device >> >> with correct keys (called here "control words") what >> >> allows to get services unscrambled. >> >> >> >> The best docu is: >> >> >> >> "Digital Video Broadcasting (DVB); >> >> Support for use of the DVB Scrambling Algorithm version 3 >> >> within digital broadcasting systems" >> >> >> >> Defined as DVB Document A125 and publicly >> >> available here: >> >> >> >> https://www.dvb.org/resources/public/standards/a125_dvb-csa3.pdf >> >> >> >> >> >> typedef struct ca_descr { >> >> unsigned int index; >> >> unsigned int parity; /* 0 == even, 1 == odd */ >> >> unsigned char cw[8]; >> >> } ca_descr_t; >> >> >> >> The 'index' is adress of the descrambler instance, as there exist >> >> limited number of them (retieved by CA_GET_DESCR_INFO). >> > >> > Thanks for the info. If I understood well, the enclosed patch should >> > be documenting it. >> > >> > >> > Thanks, >> > Mauro >> > >> > [PATCH] media: ca docs: document CA_SET_DESCR ioctl and structs >> > >> > The av7110 driver uses CA_SET_DESCR to store the descrambler >> > control words at the CA descrambler slots. >> > >> > Document it. >> > >> > Thanks-to: Honza Petrouš <jpetrous@gmail.com> >> > Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com> >> > >> > diff --git a/Documentation/media/uapi/dvb/ca-set-descr.rst b/Documentation/media/uapi/dvb/ca-set-descr.rst >> > index 9c484317d55c..a6c47205ffd8 100644 >> > --- a/Documentation/media/uapi/dvb/ca-set-descr.rst >> > +++ b/Documentation/media/uapi/dvb/ca-set-descr.rst >> > @@ -28,22 +28,11 @@ Arguments >> > ``msg`` >> > Pointer to struct :c:type:`ca_descr`. >> > >> > -.. c:type:: ca_descr >> > - >> > -.. code-block:: c >> > - >> > - struct ca_descr { >> > - unsigned int index; >> > - unsigned int parity; >> > - unsigned char cw[8]; >> > - }; >> > - >> > - >> > Description >> > ----------- >> > >> > -.. note:: This ioctl is undocumented. Documentation is welcome. >> > - >> > +CA_SET_DESCR is used for feeding descrambler CA slots with descrambling >> > +keys (refered as control words). >> > >> > Return Value >> > ------------ >> > diff --git a/include/uapi/linux/dvb/ca.h b/include/uapi/linux/dvb/ca.h >> > index f66ed53f4dc7..a62ddf0cebcd 100644 >> > --- a/include/uapi/linux/dvb/ca.h >> > +++ b/include/uapi/linux/dvb/ca.h >> > @@ -109,9 +109,16 @@ struct ca_msg { >> > unsigned char msg[256]; >> > }; >> > >> > +/** >> > + * struct ca_descr - CA descrambler control words info >> > + * >> > + * @index: CA Descrambler slot >> > + * @parity: control words parity, where 0 means even and 1 means odd >> > + * @cw: CA Descrambler control words >> > + */ >> > struct ca_descr { >> > unsigned int index; >> > - unsigned int parity; /* 0 == even, 1 == odd */ >> > + unsigned int parity; >> > unsigned char cw[8]; >> > }; >> > >> > >> >> Yeh, it should be that way. > > Good! I'll add this patch to the series. > >> BTW, the only issue I have in mind is how to link particular >> descrambler with the PID >> after your removal of the CA_SET_PID. And yes, I know that currently we have >> no any user of such ioctl in our driver base :) > > Well, I don't think that an ioctl like CA_SET_PID would solve it. > > On a generic case with is quite common nowadays on embedded hardware, > We have K demods and M CIs (where K may be different than M). > > Also, You may need to route N PIDs to O descramblers. TBH that is exactly most common use-case = most Digital TV vendors are scrambling per-service, what requires one descrambler for all scrambled PIDs (usually only A/V PIDs are scrambled) for particular service. So we have to add more PIDs to one descrambler What was possible by multiple call of CA_SET_PID (I agree that much better would be name like CA_ADD_PID) > > As user switch channels, the N PIDs should be unset, and another > set of N' pids will be routed. > > CA_SET_PID allows to set just one PID, without identifying from > what demod it would be received, and doesn't have a "reset" > function to undo. Here I can agree - it looks like the value -1 in 'index' should do the job, but it, unfortunately, looses info from which descrambler it should be removed (see note in struct ca_pid for value -1) > > So, IMHO, the interface is broken by design. Perhaps that's > the reason why no upstream driver uses it. I have the same feeling regarding brokenness. > > What seems to be a much better design would be to use the demux > set filter ioctls and route the PIDs to the right CA. > I don't have access to any programmer reference documentation for any modern DVB-enabled SoC, but I see two possible scenario of connecting descramblers to the demuxes (most of modern SoCs have more then one demux) - static one, when every demux has predefined descramblers already connected to it and dynamic ones, when any descrambler can be connected to the any demux. From that reason I vote to have some descrambler specific ioctl, which allow more flexibility then if we add it to the filter set ioctl. My 5 cents /Honza PS: I understand that until we get some multi-descrambler device included, we don't need to address descrambler management.
Em Mon, 4 Sep 2017 11:40:59 +0200 Honza Petrouš <jpetrous@gmail.com> escreveu: > > So, IMHO, the interface is broken by design. Perhaps that's > > the reason why no upstream driver uses it. > > I have the same feeling regarding brokenness. > > > > > What seems to be a much better design would be to use the demux > > set filter ioctls and route the PIDs to the right CA. > > > > I don't have access to any programmer reference documentation > for any modern DVB-enabled SoC, but I see two possible scenario > of connecting descramblers to the demuxes (most of modern SoCs > have more then one demux) - static one, when every demux has > predefined descramblers already connected to it and dynamic ones, > when any descrambler can be connected to the any demux. I don't have access to the documentation either, but I know some designs that have multiple demods that are dynamically set. Some hardware even allow to dynamically change the maximum amount of filters per demod at runtime. > From that reason I vote to have some descrambler specific ioctl, > which allow more flexibility then if we add it to the filter set ioctl. I suspect that doing it at the demod does a lot more sense. Anyway, someone should come with a driver requiring it upstream for us to discuss and find the better alternatives to support. Thanks, Mauro
diff --git a/Documentation/media/uapi/dvb/ca-set-descr.rst b/Documentation/media/uapi/dvb/ca-set-descr.rst index 9c484317d55c..a6c47205ffd8 100644 --- a/Documentation/media/uapi/dvb/ca-set-descr.rst +++ b/Documentation/media/uapi/dvb/ca-set-descr.rst @@ -28,22 +28,11 @@ Arguments ``msg`` Pointer to struct :c:type:`ca_descr`. -.. c:type:: ca_descr - -.. code-block:: c - - struct ca_descr { - unsigned int index; - unsigned int parity; - unsigned char cw[8]; - }; - - Description ----------- -.. note:: This ioctl is undocumented. Documentation is welcome. - +CA_SET_DESCR is used for feeding descrambler CA slots with descrambling +keys (refered as control words). Return Value ------------ diff --git a/include/uapi/linux/dvb/ca.h b/include/uapi/linux/dvb/ca.h index f66ed53f4dc7..a62ddf0cebcd 100644 --- a/include/uapi/linux/dvb/ca.h +++ b/include/uapi/linux/dvb/ca.h @@ -109,9 +109,16 @@ struct ca_msg { unsigned char msg[256]; }; +/** + * struct ca_descr - CA descrambler control words info + * + * @index: CA Descrambler slot + * @parity: control words parity, where 0 means even and 1 means odd + * @cw: CA Descrambler control words + */ struct ca_descr { unsigned int index; - unsigned int parity; /* 0 == even, 1 == odd */ + unsigned int parity; unsigned char cw[8]; };