Oliver:
I did a little testing. You are right that we will run into problems
with card readers that don't properly track media changes while at low
power. Going through all the partition/volume ID/RAID detection stuff
every few seconds (thanks to hal's polling) would be a real drain.
To avoid these problems, I changed sd to make it autosuspend only when
the device file is closed _and_ there is no medium present. The patch
below is just a proof-of-principle; in the end we'll want something
more flexible. Maybe a sysfs attribute to select the conditions under
which autosuspend is allowed.
What do you think?
Alan Stern
Index: usb-2.6/drivers/scsi/sd.c
===================================================================
--- usb-2.6.orig/drivers/scsi/sd.c
+++ usb-2.6/drivers/scsi/sd.c
@@ -759,9 +759,12 @@ static int sd_open(struct block_device *
sdev = sdkp->device;
- retval = scsi_autopm_get_device(sdev);
- if (retval)
- goto error_autopm;
+ /* We autosuspended iff no medium was present */
+ if (!sdkp->media_present) {
+ retval = scsi_autopm_get_device(sdev);
+ if (retval)
+ goto error_autopm;
+ }
/*
* If the device is in error recovery, wait until it is done.
@@ -807,7 +810,8 @@ static int sd_open(struct block_device *
return 0;
error_out:
- scsi_autopm_put_device(sdev);
+ if (!sdkp->media_present)
+ scsi_autopm_put_device(sdev);
error_autopm:
scsi_disk_put(sdkp);
return retval;
@@ -841,7 +845,8 @@ static int sd_release(struct gendisk *di
* XXX is followed by a "rmmod sd_mod"?
*/
- scsi_autopm_put_device(sdev);
+ if (!sdkp->media_present)
+ scsi_autopm_put_device(sdev);
scsi_disk_put(sdkp);
return 0;
}
@@ -2247,7 +2252,8 @@ static void sd_probe_async(void *data, a
sd_printk(KERN_NOTICE, sdkp, "Attached SCSI %sdisk\n",
sdp->removable ? "removable " : "");
- scsi_autopm_put_device(sdp);
+ if (!sdkp->media_present)
+ scsi_autopm_put_device(sdp);
put_device(&sdkp->dev);
}
@@ -2368,7 +2374,8 @@ static int sd_remove(struct device *dev)
struct scsi_disk *sdkp;
sdkp = dev_get_drvdata(dev);
- scsi_autopm_get_device(sdkp->device);
+ if (!sdkp->media_present)
+ scsi_autopm_get_device(sdkp->device);
async_synchronize_full();
blk_queue_prep_rq(sdkp->device->request_queue, scsi_prep_fn);
--
To unsubscribe from this list: send the line "unsubscribe linux-usb" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
