Re: IBM HDAPS things are looking up (was: Re: [Hdaps-devel] Re: [ltp] IBM HDAPS Someone interested? (Accelerometer))

[Jens Axboe <axboe@suse.de>]

On Mon, Jul 04 2005, Lenz Grimmer wrote:
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> 
> Hi,
> 
> Jens Axboe wrote:
> 
> > It isn't too pretty to rely on such unreliable timing anyways. I'm 
> > not too crazy about spinning the disk down either, it's useless wear 
> > compared to just parking the head.
> 
> Fully agreed, and that's the approach the IBM Windows driver seems to
> take - you just hear the disk park its head when the sensor kicks in
> (you can hear it) - the disk does not spin down when this happens.
> 
> Could this be some reserved ATA command that only works with certain#
> drives?

Perhaps the IDLE or IDLEIMMEDIATE commands imply a head parking, that
would make sense. As you say, you can hear a drive parking its head.
Here's a test case, it doesn't sound like it's parking the hard here.

#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/hdreg.h>

int main(int argc, char *argv[])
{
	char cmd[4] = { 0xe1, 0, 0, 0 };
	int fd;

	if (argc < 2) {
		printf("%s <dev>\n", argv[0]);
		return 1;
	}

	fd = open(argv[1], O_RDONLY);
	if (fd == -1) {
		perror("open");
		return 1;
	}

	if (ioctl(fd, HDIO_DRIVE_CMD, cmd))
		perror("ioctl");

	close(fd);
	return 0;
}

-- 
Jens Axboe

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