[openbeos] Re: driver stuff
- From: François Revol <revol@xxxxxxx>
- To: openbeos@xxxxxxxxxxxxx
- Date: Thu, 11 Jul 2002 11:02:07 +0200 (MEST)
Seems some ppl are flushing their mailbox =)
En réponse à David Reid <mail@xxxxxxxxxxxxxx>:
> I'd like to see us add a bcopy and the other b* functions (optimised
> nicely)
> to kernel space as they should deliver a small performance boost. Other
> than
> that, I think your idea is a good one, though bsd kernels also have
> copyin/copyout functions to get data into/out of the kernel space.
>
> With Michael being bogged down in usb land the kernel fork date seems to
> be
> moving slowly away :(
>
> david
>
> ----- Original Message -----
> From: "François Revol" <revol@xxxxxxx>
> To: <openbeos@xxxxxxxxxxxxx>
> Sent: Tuesday, April 30, 2002 8:24 PM
> Subject: [openbeos] driver stuff
>
>
> >
> > Someone on BeShare just mentionned to me the existance of a bunch of
> functions
> > in libroot that are known to belong to the kerneland PCI/ISA
> modules.
> >
> > [revol@patrick /boot/home/devel/obos/commands]$ nm
> /system/lib/libroot.so|grep isa_
> > 00055f1c T read_isa_io
> > 00055f24 T write_isa_io
> > [revol@patrick /boot/home/devel/obos/commands]$ nm
> /system/lib/libroot.so|grep pci_
> > 00055c04 T get_nth_pci_info
> > 00055be4 T read_pci_config
> > 00055bec T write_pci_config
> >
> > as I've been told, those use system calls to access thoses calls that
> are
> > presumably made against the kernel instance of the pci and isa
> modules.
> >
> > strings /system/lib/libroot.so|grep misc
> > tells nothing that would look like /dev/misc/config (the device
> driver
> listdev
> > uses to access the same calls. I've been told also those libroot
> calls
> were
> > public in R4 maybe. I would like whoever is to be implementing part
> of
> > libroot not to use the syscalls, but to open("/dev/misc/config");
> this
> would
> > be both cleaner and consistend with multi-user stuff in the future
> (easier
> to
> > chmod a device entry than it is to check the user in the syscall).
> >
> >
> > Another thing about drivers...
> > Although NewOS still uses the 2 GB kernel/ 2 GB user scheme, it isn't
> said
> it
> > won't switch away from this some day...
> >
> > I'd suggest anyone writing drivers up to now to use those simple
> macros,
> not
> > very hard, but surely will make switching easier in the future
> > (there are other issues, but most of the drivers should compile
> OoTB)
> > just put them at the top of your source (or the corresponding header
> file)
> >
> > #ifndef DONT_TOUCH_USERSPACE
> > // copy data from kernel space to user space
> > # define copy_to_user(dst, src, len) memcpy(dst, src, len)
> > // copy data from user space to kernel space
> > # define copy_from_user(dst, src, len) memcpy(dst, src, len)
> > // get a kernel address from a user address (if possible)
> > # define user_to_kernel(addr) (addr)
> > // get a user address from a kernel address (if possible)
> > # define kernel_to_user(addr) (addr)
> > #endif
> >
> > and do
> >
> > read_hook(..., char *p, ...)
> > {
> > ...
> > copy_to_user(p, my_kernel_buffer, to_copy);
> > // instead of memcpy(p, my_kernel_buffer, to_copy);
> > ...
> > }
> >
> >
> > If you have a better suggestion maybe ?
> >
> > François.
> >
>
>
>
Other related posts:
