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    SubjectRe: Patch of a new driver for kernel 2.4.x that need review
    On 09.08.2005 [09:56:27 -0700], Mark Gross wrote:
    > On Monday 08 August 2005 08:35, Mark Gross wrote:
    > > On Wednesday 06 July 2005 14:14, Mark Gross wrote:
    > > > On Wednesday 22 June 2005 08:12, Bouchard, Sebastien wrote:
    > > > > Hi,
    > > > >
    > > > > Here is a driver (only for 2.4.x) I've done to provide support
    > > > > of a hardware module (available on some ATCA board) used with
    > > > > telecom expension card on the new ATCA platform. This module
    > > > > provide redundant reference clock for telecom hardware with
    > > > > alarm handling when there is a new event (ex.: one of the ref
    > > > > clock is gone). This char driver provide IOCTL for
    > > > > configuration of this module and interrupt handler for
    > > > > processing alarm events.
    > > > >
    > > > > I send this driver so people in this mailing list can do a
    > > > > review of the code.
    > > > >
    > > > > Please reply me directly to my email, i'm not subscribed to the
    > > > > mailing list.
    > > > >
    > > > > Thanks
    > > > > Sebastien Bouchard
    > > > > Software designer
    > > > > Kontron Canada Inc.
    > > > > <mailto:sebastien.bouchard@ca.kontron.com>
    > > > > <http://www.kontron.com/>
    > > >
    > > > I'm helping out a bit with the maintaining of this driver for
    > > > Sebastien.   The following is a 2.6.12 port of Sebastien's 2.4
    > > > driver.  
    > > >
    > > > --mgross
    > >
    > > The following is an update to the earlier 2.6 driver that uses a
    > > sysfs interface to implement the IOCTL functions.  I put the
    > > attributes under /sys/class/misc/tlclk.
    > >
    > > I can't say I'm a believer in the "goodness" of using sysfs over the
    > > IOCTL's, as it added quite a bit of code bloat to this driver, but
    > > hay it should work well enough anyway.
    > >
    > > Also, note this device, is accessed / controlled via the FPGA on the
    > > ATCA, its function is to synchronize signaling hardware across
    > > blades in an ATCA Chassis.  It tends to not talk to the OS.
    > >
    > > Please tell me what you think :)
    > Again but with email word wrap turned off :(
    > Also fixes my miss use of kcalloc parameter list.

    <snip>

    > diff -urN -X dontdiff linux-2.6.12.3/drivers/char/tlclk.c linux-2.6.12.3-tlclk/drivers/char/tlclk.c
    > --- linux-2.6.12.3/drivers/char/tlclk.c 1969-12-31 16:00:00.000000000 -0800
    > +++ linux-2.6.12.3-tlclk/drivers/char/tlclk.c 2005-08-09 09:37:58.000000000 -0700

    <snip>

    > +irqreturn_t tlclk_interrupt(int irq, void *dev_id, struct pt_regs *regs)

    <snip>

    > + switchover_timer.expires = jiffies + 1; /* TIMEOUT in ~10ms */

    This is not a 10 millisecond timeout, it is a 1 jiffy timeout. Yes, in
    2.4, where HZ=100 by default, or in 2.6 with CONFIG_HZ set to 100, that
    corresponds to 10 millseconds (or so ;), but not with HZ=250 or 1000. I
    think you want:

    switchover_timer.expires = jiffies + msecs_to_jiffies(10);

    which will handle rounding correctly.

    Also, consider using TIMER_INITIALIZER() for setting these timer fields.

    <snip>

    Thanks,
    Nish
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