From cee071276c75b232ba701080b621ea7dde177cdf Mon Sep 17 00:00:00 2001
From: Sayali Lokhande <sayalil@codeaurora.org>
Date: Thu, 24 May 2018 16:18:41 +0530
Subject: [PATCH] Revert "scsi: sd: remove check_events callback"

This reverts commit fe64842c81d6b2dc34321dde12530c92d5df556b.
On auto platforms, it is observed that sdcard is not getting
detected using usb card reader as check_events callback was
removed. For usb card reader case, scsi check_events() callback
is required which sends test unit ready command to check if
underlying media state has changed. So instead of removing
check_events() completely, simply return for embedded storage
media like UFS.

Change-Id: Iefd163db1a1098c01c2dbaf441f072b07b19caca
Signed-off-by: Sayali Lokhande <sayalil@codeaurora.org>
---
 drivers/scsi/sd.c | 80 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 80 insertions(+)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 6e66e2ad9daf..367dde6a6e17 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -1420,6 +1420,85 @@ static int media_not_present(struct scsi_disk *sdkp,
 	return 0;
 }
 
+/**
+ *	sd_check_events - check media events
+ *	@disk: kernel device descriptor
+ *	@clearing: disk events currently being cleared
+ *
+ *	Returns mask of DISK_EVENT_*.
+ *
+ *	Note: this function is invoked from the block subsystem.
+ **/
+static unsigned int sd_check_events(struct gendisk *disk, unsigned int clearing)
+{
+	struct scsi_disk *sdkp = scsi_disk(disk);
+	struct scsi_device *sdp = sdkp->device;
+	struct scsi_sense_hdr *sshdr = NULL;
+	int retval;
+
+	SCSI_LOG_HLQUEUE(3, sd_printk(KERN_INFO, sdkp, "sd_check_events\n"));
+
+	/* Simply return for embedded storage media such as UFS */
+	if (!sdp->removable)
+		goto out;
+
+	/*
+	 * If the device is offline, don't send any commands - just pretend as
+	 * if the command failed.  If the device ever comes back online, we
+	 * can deal with it then.  It is only because of unrecoverable errors
+	 * that we would ever take a device offline in the first place.
+	 */
+	if (!scsi_device_online(sdp)) {
+		set_media_not_present(sdkp);
+		goto out;
+	}
+
+	/*
+	 * Using TEST_UNIT_READY enables differentiation between drive with
+	 * no cartridge loaded - NOT READY, drive with changed cartridge -
+	 * UNIT ATTENTION, or with same cartridge - GOOD STATUS.
+	 *
+	 * Drives that auto spin down. eg iomega jaz 1G, will be started
+	 * by sd_spinup_disk() from sd_revalidate_disk(), which happens whenever
+	 * sd_revalidate() is called.
+	 */
+	retval = -ENODEV;
+
+	if (scsi_block_when_processing_errors(sdp)) {
+		sshdr  = kzalloc(sizeof(*sshdr), GFP_KERNEL);
+		retval = scsi_test_unit_ready(sdp, SD_TIMEOUT, SD_MAX_RETRIES,
+					      sshdr);
+	}
+
+	/* failed to execute TUR, assume media not present */
+	if (host_byte(retval)) {
+		set_media_not_present(sdkp);
+		goto out;
+	}
+
+	if (media_not_present(sdkp, sshdr))
+		goto out;
+
+	/*
+	 * For removable scsi disk we have to recognise the presence
+	 * of a disk in the drive.
+	 */
+	if (!sdkp->media_present)
+		sdp->changed = 1;
+	sdkp->media_present = 1;
+out:
+	/*
+	 * sdp->changed is set under the following conditions:
+	 *
+	 *	Medium present state has changed in either direction.
+	 *	Device has indicated UNIT_ATTENTION.
+	 */
+	kfree(sshdr);
+	retval = sdp->changed ? DISK_EVENT_MEDIA_CHANGE : 0;
+	sdp->changed = 0;
+	return retval;
+}
+
 static int sd_sync_cache(struct scsi_disk *sdkp)
 {
 	int retries, res;
@@ -1612,6 +1691,7 @@ static const struct block_device_operations sd_fops = {
 #ifdef CONFIG_COMPAT
 	.compat_ioctl		= sd_compat_ioctl,
 #endif
+	.check_events		= sd_check_events,
 	.revalidate_disk	= sd_revalidate_disk,
 	.unlock_native_capacity	= sd_unlock_native_capacity,
 	.pr_ops			= &sd_pr_ops,