So it's not an error it's normal case ! I am happy to hear that. Thanks for your help. --- En date de : Mer 7.1.09, Belisko Marek <marek.belisko@xxxxxxxxx> a écrit : > De: Belisko Marek <marek.belisko@xxxxxxxxx> > Objet: Re: sysfs_notify & poll > À: kpa_info@xxxxxxxx > Cc: kernelnewbies@xxxxxxxxxxxx > Date: Mercredi 7 Janvier 2009, 16h26 > Hi, > > On Wed, Jan 7, 2009 at 4:20 PM, PAtrick Gerber > <kpa_info@xxxxxxxx> wrote: > > I found some occurences of sysfs_notify in different > driver (phidgetkit driver for example). > > > > As I sayd in my previous post now it's working. I > can start poll on my attribute (sysfs file) and when I > execute sysfs_notify in my driver the event is handled by > poll. But I have still a little probleme, the poll call > return POLLPRI and POLLERR. Only POLLPRI is normal I > don't understand why we have both ??? > > Sorry I miss your previous mail. In article which I send > you a link is > mentioned: > user space need only open the attribute of interest pass it > to poll() > with the POLLERR and POLLPRI events selected. When poll() > returns, the > file can be reopened and reread to obtain the new value. > > If you look to sysfs_poll it returns POLLERR|POLLPRI. You > can't use POLLERR. > Godd to hear it's working ;). > > > > > Any idea ? > > > > > > > > --- En date de : Mer 7.1.09, Belisko Marek > <marek.belisko@xxxxxxxxx> a écrit : > > > >> De: Belisko Marek <marek.belisko@xxxxxxxxx> > >> Objet: Re: sysfs_notify & poll > >> À: kpa_info@xxxxxxxx > >> Date: Mercredi 7 Janvier 2009, 15h46 > >> Hi, > >> > >> On Wed, Jan 7, 2009 at 3:25 PM, PAtrick Gerber > >> <kpa_info@xxxxxxxx> wrote: > >> > I am not sure but I had understanded that we > need to > >> implement the pool syscall, as described in ldd3 > books, only > >> for chardevices. For attributes in sysfs, the poll > syscall > >> is managed by the kernel/sysfs and we can simply > use > >> sysfs_notify on the kernel side. An event queue is > managed > >> for each attribute for this purprose. > >> I think sysfs_notify couldn't be called from > >> kobject-example. If you > >> search through whole kernel tree > >> no occurences only in sysfs/file.c is found. > >> > >> You can read this article > (http://lwn.net/Articles/174660/) > >> and try > >> what's described. > >> If poll returns close file and open again. New > value should > >> be obtained. > >> > > >> > But as I say before I am not clear with this. > You can > >> read this : > >> > http://lists.linuxcoding.com/kernel/2006-q1/msg28166.html or > >> this from the kernel source: > >> > > >> > /* Sysfs attribute files are pollable. The > idea is > >> that you read > >> > * the content and then you use > 'poll' or > >> 'select' to wait for > >> > * the content to change. When the content > changes > >> (assuming the > >> > * manager for the kobject supports > notification), > >> poll will > >> > * return POLLERR|POLLPRI, and select will > return the > >> fd whether > >> > * it is waiting for read, write, or > exceptions. > >> > * Once poll/select indicates that the value > has > >> changed, you > >> > * need to close and re-open the file, as > simply > >> seeking and reading > >> > * again will not get new data, or reset the > state of > >> 'poll'. > >> > * Reminder: this only works for attributes > which > >> actively support > >> > * it, and it is not possible to test an > attribute > >> from userspace > >> > * to see if it supports poll (Nether > 'poll' > >> or 'select' return > >> > * an appropriate error code). When in > doubt, set a > >> suitable timeout value. > >> > */ > >> > > >> > > >> > --- En date de : Mer 7.1.09, Belisko Marek > >> <marek.belisko@xxxxxxxxx> a écrit : > >> > > >> >> De: Belisko Marek > <marek.belisko@xxxxxxxxx> > >> >> Objet: Re: sysfs_notify & poll > >> >> À: "PAtrick Gerber" > >> <kpa_info@xxxxxxxx> > >> >> Cc: kernelnewbies@xxxxxxxxxxxx > >> >> Date: Mercredi 7 Janvier 2009, 15h09 > >> >> Hi, > >> >> > >> >> On Wed, Jan 7, 2009 at 2:21 PM, PAtrick > Gerber > >> >> <kpa_info@xxxxxxxx> wrote: > >> >> > Thanks for the information. > >> >> > > >> >> > I have tested with the example from > >> >> http://linux.die.net/man/3/poll slightly > modified > >> (see the > >> >> attached file). > >> >> > If I test pool on the > >> >> > "/sys/module/systest/sections/.data" > >> file it seems > >> >> to work fine. But if I try the same test > >> application with my > >> >> attribute > (/sys/kernel/kobject_example/bar) > >> created with the > >> >> example from linux sources > >> >> (samples/kobject/kobject_example.c) the > result is > >> an event > >> >> POLLERR. > >> >> > >> >> > > >> >> > Do you have any idea why ? Need I to > add > >> special code > >> >> for support poll syscall in my driver ? > >> >> Of course you should implement poll > syscall in > >> kernel > >> >> driver. But for > >> >> kobject-example it could be a problem > >> >> because you don't have a file > operations in > >> this > >> >> example. But thats > >> >> only my feeling ;) > >> >> Example for poll : (ldd3 > >> >> http://lwn.net/images/pdf/LDD3/ch06.pdf ) > >> >> > > >> >> > Thanks in advance > >> >> > > >> >> > --- En date de : Mer 7.1.09, Belisko > Marek > >> >> <marek.belisko@xxxxxxxxx> a écrit > : > >> >> > > >> >> >> De: Belisko Marek > >> <marek.belisko@xxxxxxxxx> > >> >> >> Objet: Re: sysfs_notify & > poll > >> >> >> À: "PAtrick Gerber" > >> >> <kpa_info@xxxxxxxx> > >> >> >> Date: Mercredi 7 Janvier 2009, > 13h59 > >> >> >> Hi, > >> >> >> > >> >> >> On Wed, Jan 7, 2009 at 1:54 PM, > PAtrick > >> Gerber > >> >> >> <kpa_info@xxxxxxxx> wrote: > >> >> >> > Ok thanks. Usefull example. > But I > >> have > >> >> another > >> >> >> question: > >> >> >> > > >> >> >> > Need I to use poll or epoll > ? I dont > >> really > >> >> understand > >> >> >> the difference. > >> >> >> epoll is a variant of poll that > can be > >> used either > >> >> as Edge > >> >> >> or Level > >> >> >> Triggered interface and scales > well to > >> large > >> >> numbers of > >> >> >> watched fds. > >> >> >> For beginnig you can use normal > poll > >> syscall. > >> >> >> > >> >> >> > > >> >> >> > Thanks in advance for any > help ! > >> >> >> > > >> >> >> > On Wed, Jan 7, 2009 at 9:40 > AM, > >> PAtrick > >> >> Gerber > >> >> >> <kpa_info@xxxxxxxx> wrote: > >> >> >> >> Hello, > >> >> >> >> > >> >> >> >> I would like to try to > use > >> sysfs_notify() > >> >> / poll() > >> >> >> mechanism from my > >> >> >> > driver > >> >> >> >> to notify some events > to my > >> application. > >> >> I'm > >> >> >> looking for a tiny > >> >> >> > example > >> >> >> >> showing the use of this > >> mechanism. > >> >> >> >> > >> >> >> >> The driver side with > >> sysfs_notify seems > >> >> quite > >> >> >> simple but I have absolutely > >> >> >> >> no idea about the > application > >> side. > >> >> >> > > >> >> >> > Fo poll method you canfind > good > >> description > >> >> and also > >> >> >> example at: > >> >> >> > > http://linux.die.net/man/3/poll > >> >> >> > > >> >> >> >> > >> >> >> >> Thanks in advance > >> >> >> >> > >> >> >> >> Patrick > >> >> >> >> > >> >> >> > > >> >> >> > thanks, > >> >> >> > > >> >> >> > Marek > >> >> >> > > >> >> >> > > >> >> >> > > >> >> >> > > >> >> >> > > >> >> >> > > >> >> >> > > >> >> >> > >> >> >> thanks, > >> >> >> > >> >> >> Marek > >> >> >> > >> >> >> -- > >> >> >> as simple as primitive as > possible > >> >> >> > >> ---------------------------------------------- > >> >> >> Marek Beliško - open-nandra > >> >> >> Ruská Nová Ves 219 > >> >> >> 08005 Prešov > >> >> >> Slovakia > >> >> >> http://open-nandra.com > >> >> > > >> >> > > >> >> > > >> >> > >> >> thanks, > >> >> > >> >> Marek > >> >> > >> >> -- > >> >> as simple as primitive as possible > >> >> > ---------------------------------------------- > >> >> Marek Beliško - open-nandra > >> >> Ruská Nová Ves 219 > >> >> 08005 Prešov > >> >> Slovakia > >> >> http://open-nandra.com > >> > > >> > > >> > > >> > > >> > >> thanks, > >> > >> Marek > >> > >> > >> -- > >> as simple as primitive as possible > >> ---------------------------------------------- > >> Marek Beliško - open-nandra > >> Ruská Nová Ves 219 > >> 08005 Prešov > >> Slovakia > >> http://open-nandra.com > > > > > > > > > > > Marek > -- > as simple as primitive as possible > ---------------------------------------------- > Marek Beliško - open-nandra > Ruská Nová Ves 219 > 08005 Prešov > Slovakia > http://open-nandra.com -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
