Date: Tue, 28 Aug 2012 13:38:13 -0400 From: John Baldwin <jhb@freebsd.org> To: Konstantin Belousov <kostikbel@gmail.com> Cc: freebsd-current@freebsd.org, Luigi Rizzo <rizzo@iet.unipi.it>, current@freebsd.org, Andriy Gapon <avg@freebsd.org> Subject: Re: per file descriptor device callbacks ? Message-ID: <201208281338.13612.jhb@freebsd.org> In-Reply-To: <20120828172606.GR33100@deviant.kiev.zoral.com.ua> References: <20120827073403.GA49223@onelab2.iet.unipi.it> <201208281240.29612.jhb@freebsd.org> <20120828172606.GR33100@deviant.kiev.zoral.com.ua>
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On Tuesday, August 28, 2012 1:26:06 pm Konstantin Belousov wrote: > On Tue, Aug 28, 2012 at 12:40:29PM -0400, John Baldwin wrote: > > On Tuesday, August 28, 2012 11:50:25 am Luigi Rizzo wrote: > > > On Mon, Aug 27, 2012 at 12:27:54PM -0400, John Baldwin wrote: > > > > On Monday, August 27, 2012 3:55:47 am Andriy Gapon wrote: > > > > > on 27/08/2012 10:34 Luigi Rizzo said the following: > > > > > > This requires to track calls to open/ioctl/poll/mmap/close. > > > > > > The difficulty i have is with mmap() and close(), because FreeBSD > > > > > > seems to handle these calls per-cdev rather than per-file-descriptor > > > > > > (for instance, no 'struct file' argument is available in mmap(), and > > > > > > the d_close method is only called on the last close() on the device). > > > > > > > > > > devfs_set_cdevpriv(9), etc > > > > > > > > mmap() is still problematic, but if you have the freedom to create your > > > > own VM objects, then d_mmap_single() can let you handle that fairly > > > > easily. > > > > > > Would dev_clone(9) be a better way to do what i need ? > > > > > > This way the struct cdev would be unique per file descriptor, > > > could be used as a key on the page fault callbacks > > > (i still do not have callbacks on dev_pager_ctor/dtor though). > > > > dev_clone() is rather gross and a lot harder to use than > > devfs_set_cdevpriv(). If you are fine with the inherent problems > > of the device pager (you can't ever make mappings go away), you can > > just assign each client a unique offset into your shared object's > > memory space. However, if you are exporting shared memory buffers, > > then a better model might be to let your clients use > > shm_open(SHM_ANON) to create buffers, then pass them into your driver > > via an ioctl() and use shm_map() to map them into the kernel. > > Well, there is a new OBJT_MGTDEVICE pager, which together with > d_mmap_single() allows to have even per-mapping data. i915kms uses it. > You do not need cdevpriv for the per-mapping data. > > Also, MGTDEVICE does track the mappings of the pages, so you can clean > up on device destruction. > > Normal callbacks of the device pager allows to execute ctr/dtr methods > at the time of mapping creation and tear down. These pages create PV entries so you can invalidate mappings when you invalidate a backing object, yes? That is part of the problem with the standard device pager (no way to invalidate existing mappings of an object). -- John Baldwin
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