On Mon, 2011-06-13 at 21:02 +0200, Kay Sievers wrote:
> We follow GET_EVENT_STATUS_NOTIFICATION now. Can't we always force TUR
> when we open() the device from userland? That's what we did in the
> past, didn't we? The in-kernel polling would still not need to do
> that, and the periodic usespace polling is about to die pretty soon.
After the long discussion today between Tejun and me, something like
this *could* work. A patch with printk() debug output is below.
Every open() from userland does: GET_EVENT_STATUS_NOTIFICATION and TUR.
If the both results disagree 8 times in a row, we will only look at the
TUR results in the future.
With this I get in dmesg:
scsi 8:0:0:1: CD-ROM SanDisk U3 Cruzer Micro 8.02 PQ: 0 ANSI: 0
sr1: scsi3-mmc drive: 48x/48x tray
sr 8:0:0:1: Attached scsi CD-ROM sr1
sr 8:0:0:1: Attached scsi generic sg3 type 5
sr: GET_EVENT_STATUS_NOTIFICATION but TUR unchanged, last_present 1 <-> cd->media_present 1, count 1
sr: GET_EVENT_STATUS_NOTIFICATION but TUR unchanged, last_present 1 <-> cd->media_present 1, count 2
sr: GET_EVENT_STATUS_NOTIFICATION but TUR unchanged, last_present 1 <-> cd->media_present 1, count 3
sr: GET_EVENT_STATUS_NOTIFICATION but TUR unchanged, last_present 1 <-> cd->media_present 1, count 4
sr: GET_EVENT_STATUS_NOTIFICATION but TUR unchanged, last_present 1 <-> cd->media_present 1, count 5
sr: GET_EVENT_STATUS_NOTIFICATION but TUR unchanged, last_present 1 <-> cd->media_present 1, count 6
sr: GET_EVENT_STATUS_NOTIFICATION but TUR unchanged, last_present 1 <-> cd->media_present 1, count 7
sr: GET_EVENT_STATUS_NOTIFICATION but TUR unchanged, last_present 1 <-> cd->media_present 1, count 8
sr: GET_EVENT_STATUS_NOTIFICATION but TUR unchanged, last_present 1 <-> cd->media_present 1, count 9
sr: GET_EVENT_STATUS_NOTIFICATION but TUR unchanged, ignoring all future GET_EVENT_STATUS_NOTIFICATION
The in-kernel polling will still create a media change event every poll
interval. The rest seems to work as expected.
The other properly working devices I tried fail with the very first TUR
<-> GET_EVENT check for some reason:
scsi 7:0:0:0: CD-ROM TSSTcorp CDDVDW SE-S084B TS01 PQ: 0 ANSI: 0
sr2: scsi3-mmc drive: 8x/24x writer dvd-ram cd/rw xa/form2 cdda tray
sr 7:0:0:0: Attached scsi CD-ROM sr2
sr 7:0:0:0: Attached scsi generic sg4 type 5
sr: GET_EVENT_STATUS_NOTIFICATION but TUR unchanged, last_present 1 <-> cd->media_present 1, count 1
sr: GET_EVENT_STATUS_NOTIFICATION == TUR, clear mismatch count 1
Everything thing else seems to work fine.
Kay
---
diff --git a/drivers/scsi/sr.c b/drivers/scsi/sr.c
index 4778e27..9023e1d 100644
--- a/drivers/scsi/sr.c
+++ b/drivers/scsi/sr.c
@@ -229,6 +229,15 @@ static unsigned int sr_check_events(struct cdrom_device_info *cdi,
if (!(clearing & DISK_EVENT_MEDIA_CHANGE))
goto skip_tur;
+ /*
+ * earlier GET_EVENT_STATUS_NOTIFICATION and TUR did not agree
+ * for a couple of times in a row, we rely on TUR only for this
+ * likely broken device, to prevent generating incorrect media
+ * changed events for every open()
+ */
+ if (cd->ignore_get_event)
+ events = 0;
+
/* let's see whether the media is there with TUR */
last_present = cd->media_present;
ret = scsi_test_unit_ready(cd->device, SR_TIMEOUT, MAX_RETRIES, &sshdr);
@@ -241,8 +250,22 @@ static unsigned int sr_check_events(struct cdrom_device_info *cdi,
cd->media_present = scsi_status_is_good(ret) ||
(scsi_sense_valid(&sshdr) && sshdr.asc != 0x3a);
- if (last_present != cd->media_present)
+ if (last_present != cd->media_present) {
events |= DISK_EVENT_MEDIA_CHANGE;
+ } else if (events & DISK_EVENT_MEDIA_CHANGE) {
+ cd->tur_mismatch++;
+ printk("sr: GET_EVENT_STATUS_NOTIFICATION but TUR unchanged, "
+ "last_present %i <-> cd->media_present %i, count %i\n", last_present, cd->media_present, cd->tur_mismatch);
+ if (cd->tur_mismatch > 8) {
+ printk("sr: GET_EVENT_STATUS_NOTIFICATION but TUR unchanged, "
+ "ignoring all future GET_EVENT_STATUS_NOTIFICATION\n");
+ cd->ignore_get_event = true;
+ }
+ } else if (cd->tur_mismatch) {
+ printk("sr: GET_EVENT_STATUS_NOTIFICATION == TUR, "
+ "clear mismatch count %i\n", cd->tur_mismatch);
+ cd->tur_mismatch = 0;
+ }
skip_tur:
if (cd->device->changed) {
events |= DISK_EVENT_MEDIA_CHANGE;
diff --git a/drivers/scsi/sr.h b/drivers/scsi/sr.h
index e036f1d..94a3215 100644
--- a/drivers/scsi/sr.h
+++ b/drivers/scsi/sr.h
@@ -41,6 +41,8 @@ typedef struct scsi_cd {
unsigned readcd_known:1; /* drive supports READ_CD (0xbe) */
unsigned readcd_cdda:1; /* reading audio data using READ_CD */
unsigned media_present:1; /* media is present */
+ unsigned ignore_get_event:1; /* get_event is unreliable, use TUR */
+ int tur_mismatch; /* nr of get_event TUR mismatches */
struct cdrom_device_info cdi;
/* We hold gendisk and scsi_device references on probe and use
* the refs on this kref to decide when to release them */
--
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