Date: Mon, 8 Sep 2008 17:29:34 -0400 From: John Baldwin <jhb@freebsd.org> To: freebsd-current@freebsd.org Cc: Kostik Belousov <kostikbel@gmail.com>, Robert Watson <rwatson@freebsd.org>, vehemens <vehemens@verizon.net> Subject: Re: bsd versus linux device drivers Message-ID: <200809081729.35340.jhb@freebsd.org> In-Reply-To: <alpine.BSF.1.10.0809081434200.37494@fledge.watson.org> References: <200809080202.00664.vehemens@verizon.net> <200809080350.41579.vehemens@verizon.net> <alpine.BSF.1.10.0809081434200.37494@fledge.watson.org>
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On Monday 08 September 2008 09:41:53 am Robert Watson wrote:
> On Mon, 8 Sep 2008, vehemens wrote:
> > On Monday 08 September 2008 03:04:15 am Kostik Belousov wrote:
> >> On Mon, Sep 08, 2008 at 02:02:00AM -0700, vehemens wrote:
> >>> In linux drivers, there is a one to one relationship to an open and a
> >>> calling argument structure called struct file. It provides a private
> >>> data pointer that allows the driver to preserve unique state
> >>> information across other calls such as read/write/ioctl/mmap/close etc.
> >>>
> >>> For bsd drivers, my understanding there is not an equivalent. As a
> >>> result it is not possible to preserve different state information for
> >>> multiple opens by the same thread of the same device major/minor #'s.
> >>>
> >>> Is this correct, or did i miss something?
> >>
> >> There is devfs_{get,set}_cdevpriv() KPI. Still no manpage, I shall fix
> >> this ASAP.
> >
> > Just started looking at the firewire driver which has clone. It looks
> > like it hooks into the event handler.
> >
> > Don't quite understand it all yet, so I'm going to look forward to that
> > man page.
>
> Many device drivers continue to use the old clone interface, but are
> gradually being converted over. You can look at the definitions and list
> of converted drivers here:
>
> http://fxr.watson.org/fxr/ident?im=bigexcerpts;i=devfs_set_cdevpriv
>
> Looking at some of the converted drivers, I find myself a bit worried by
> the extra error handling: in what situations do we expect that bpfioctl()
> might be called without its cdev-private data?
I think that is just hyper-paranoia.
--
John Baldwin
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