linux-kernel - Re: [GIT PATCH] more Driver core patches for 2.6.19

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Message-ID: <Pine.LNX.4.61.0612141206500.6223@yvahk01.tjqt.qr>
Date:	Thu, 14 Dec 2006 12:18:23 +0100 (MET)
From:	Jan Engelhardt <jengelh@...ux01.gwdg.de>
To:	Linus Torvalds <torvalds@...l.org>
cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Greg KH <gregkh@...e.de>, Andrew Morton <akpm@...l.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [GIT PATCH] more Driver core patches for 2.6.19


>> For the sharing case, some sort of softirq should be created. That is, when a
>> hard interrupt is generated and the irq handler is executed, set a flag that at
>> some other point in time, the irq is delivered to userspace. Like you do with
>> signals in userspace:
>
>NO.
>
>The whole point is, YOU CANNOT DO THIS.
>
>You need to shut the device up. Otherwise it keeps screaming.
>
>Please, people, don't confuse the issue any further. A hardware driver
>
>	ABSOLUTELY POSITIVELY HAS TO
>
>have an in-kernel irq handler that knows how to turn the irq off.
>
>End of story. No ifs, buts, maybes about it.

I don't get you. The rtc module does something similar (RTC generates
interrupts and notifies userspace about it)


  irqreturn_t uio_handler(...) {
      disable interrupts for this dev;
      set a flag that notifies userspace the next best time;
      seomstruct->flag |= IRQ_ARRIVED;
      return IRQ_HANDLED;
  }


  /* Userspace->kernel notification, e.g. by means of a device node
     /dev/uio or some ioctl. */
  int uio_write(...) {
      somestruct->flag &= ~IRQ_ARRIVED;
      enable interrupts for the device;
  }



> - have an in-kernel irq handler that at a minimum knows how to test 
>   whether the irq came from that device and knows how to shut it up.
>
>This means NOT A GENERIC DRIVER. That simply isn't an option on the 
>table, no matter how much people would like it to be.


	-`J'
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