[PATCH v2] scsi_debug: add cdb_len paramete

[Douglas Gilbert <dgilbert@interlog.com>]

While testing "sd: Micro-optimize READ / WRITE CDB encoding" patches it was
helpful to check various code paths associated with READ/WRITE 6, 10
and 16 byte cdb variants. There seems to be no user space "knobs" to
twiddle use_10_for_rw and friends in the scsi_device structure.
So add a parameter to scsi_debug called "cdb_len" for this purpose.

Changes since v1:
  - address most of the concerns from Bart Van Assche
  - keep driver version and date and tie them into some responses
    (e.g. version becomes INQUIRY Revision field)

Patch built on lk 4.15.0-rc2

Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
---
 drivers/scsi/scsi_debug.c | 92 ++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 87 insertions(+), 5 deletions(-)

diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index e4f037f0f38b..691ce8f37d34 100644
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -6,7 +6,7 @@
  *  anything out of the ordinary is seen.
  * ^^^^^^^^^^^^^^^^^^^^^^^ Original ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  *
- * Copyright (C) 2001 - 2016 Douglas Gilbert
+ * Copyright (C) 2001 - 2017 Douglas Gilbert
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -61,8 +61,8 @@
 #include "scsi_logging.h"
 
 /* make sure inq_product_rev string corresponds to this version */
-#define SDEBUG_VERSION "1.86"
-static const char *sdebug_version_date = "20160430";
+#define SDEBUG_VERSION "0187"	/* format to fit INQUIRY revision field */
+static const char *sdebug_version_date = "20171202";
 
 #define MY_NAME "scsi_debug"
 
@@ -105,6 +105,7 @@ static const char *sdebug_version_date = "20160430";
  * (id 0) containing 1 logical unit (lun 0). That is 1 device.
  */
 #define DEF_ATO 1
+#define DEF_CDB_LEN 10
 #define DEF_JDELAY   1		/* if > 0 unit is a jiffy */
 #define DEF_DEV_SIZE_MB   8
 #define DEF_DIF 0
@@ -571,6 +572,7 @@ static const struct opcode_info_t opcode_info_arr[SDEB_I_LAST_ELEMENT + 1] = {
 
 static int sdebug_add_host = DEF_NUM_HOST;
 static int sdebug_ato = DEF_ATO;
+static int sdebug_cdb_len = DEF_CDB_LEN;
 static int sdebug_jdelay = DEF_JDELAY;	/* if > 0 then unit is jiffies */
 static int sdebug_dev_size_mb = DEF_DEV_SIZE_MB;
 static int sdebug_dif = DEF_DIF;
@@ -797,6 +799,61 @@ static int scsi_debug_ioctl(struct scsi_device *dev, int cmd, void __user *arg)
 	/* return -ENOTTY; // correct return but upsets fdisk */
 }
 
+static void config_cdb_len(struct scsi_device *sdev)
+{
+	switch (sdebug_cdb_len) {
+	case 6:	/* suggest 6 byte READ, WRITE and MODE SENSE/SELECT */
+		sdev->use_10_for_rw = false;
+		sdev->use_16_for_rw = false;
+		sdev->use_10_for_ms = false;
+		break;
+	case 10: /* suggest 10 byte RWs and 6 byte MODE SENSE/SELECT */
+		sdev->use_10_for_rw = true;
+		sdev->use_16_for_rw = false;
+		sdev->use_10_for_ms = false;
+		break;
+	case 12: /* suggest 10 byte RWs and 10 byte MODE SENSE/SELECT */
+		sdev->use_10_for_rw = true;
+		sdev->use_16_for_rw = false;
+		sdev->use_10_for_ms = true;
+		break;
+	case 16:
+		sdev->use_10_for_rw = false;
+		sdev->use_16_for_rw = true;
+		sdev->use_10_for_ms = true;
+		break;
+	case 32: /* No knobs to suggest this so same as 16 for now */
+		sdev->use_10_for_rw = false;
+		sdev->use_16_for_rw = true;
+		sdev->use_10_for_ms = true;
+		break;
+	default:
+		pr_warn("unexpected cdb_len=%d, force to 10\n",
+			sdebug_cdb_len);
+		sdev->use_10_for_rw = true;
+		sdev->use_16_for_rw = false;
+		sdev->use_10_for_ms = false;
+		sdebug_cdb_len = 10;
+		break;
+	}
+}
+
+static void all_config_cdb_len(void)
+{
+	struct sdebug_host_info *sdbg_host;
+	struct Scsi_Host *shost;
+	struct scsi_device *sdev;
+
+	spin_lock(&sdebug_host_list_lock);
+	list_for_each_entry(sdbg_host, &sdebug_host_list, host_list) {
+		shost = sdbg_host->shost;
+		shost_for_each_device(sdev, shost) {
+			config_cdb_len(sdev);
+		}
+	}
+	spin_unlock(&sdebug_host_list_lock);
+}
+
 static void clear_luns_changed_on_target(struct sdebug_dev_info *devip)
 {
 	struct sdebug_host_info *sdhp;
@@ -955,7 +1012,7 @@ static int fetch_to_dev_buffer(struct scsi_cmnd *scp, unsigned char *arr,
 
 static char sdebug_inq_vendor_id[9] = "Linux   ";
 static char sdebug_inq_product_id[17] = "scsi_debug      ";
-static char sdebug_inq_product_rev[5] = "0186";	/* version less '.' */
+static char sdebug_inq_product_rev[5] = SDEBUG_VERSION;
 /* Use some locally assigned NAAs for SAS addresses. */
 static const u64 naa3_comp_a = 0x3222222000000000ULL;
 static const u64 naa3_comp_b = 0x3333333000000000ULL;
@@ -1411,6 +1468,8 @@ static int resp_inquiry(struct scsi_cmnd *scp, struct sdebug_dev_info *devip)
 	memcpy(&arr[8], sdebug_inq_vendor_id, 8);
 	memcpy(&arr[16], sdebug_inq_product_id, 16);
 	memcpy(&arr[32], sdebug_inq_product_rev, 4);
+	/* Use Vendor Specific area to place driver date in ASCII hex */
+	memcpy(&arr[36], sdebug_version_date, 8);
 	/* version descriptors (2 bytes each) follow */
 	put_unaligned_be16(0xc0, arr + 58);   /* SAM-6 no version claimed */
 	put_unaligned_be16(0x5c0, arr + 60);  /* SPC-5 no version claimed */
@@ -3660,6 +3719,7 @@ static int scsi_debug_slave_configure(struct scsi_device *sdp)
 	blk_queue_max_segment_size(sdp->request_queue, -1U);
 	if (sdebug_no_uld)
 		sdp->no_uld_attach = 1;
+	config_cdb_len(sdp);
 	return 0;
 }
 
@@ -4141,6 +4201,7 @@ static int schedule_resp(struct scsi_cmnd *cmnd, struct sdebug_dev_info *devip,
  */
 module_param_named(add_host, sdebug_add_host, int, S_IRUGO | S_IWUSR);
 module_param_named(ato, sdebug_ato, int, S_IRUGO);
+module_param_named(cdb_len, sdebug_cdb_len, int, 0644);
 module_param_named(clustering, sdebug_clustering, bool, S_IRUGO | S_IWUSR);
 module_param_named(delay, sdebug_jdelay, int, S_IRUGO | S_IWUSR);
 module_param_named(dev_size_mb, sdebug_dev_size_mb, int, S_IRUGO);
@@ -4198,6 +4259,7 @@ MODULE_VERSION(SDEBUG_VERSION);
 
 MODULE_PARM_DESC(add_host, "0..127 hosts allowed(def=1)");
 MODULE_PARM_DESC(ato, "application tag ownership: 0=disk 1=host (def=1)");
+MODULE_PARM_DESC(cdb_len, "suggest CDB lengths to drivers (def=10)");
 MODULE_PARM_DESC(clustering, "when set enables larger transfers (def=0)");
 MODULE_PARM_DESC(delay, "response delay (def=1 jiffy); 0:imm, -1,-2:tiny");
 MODULE_PARM_DESC(dev_size_mb, "size in MiB of ram shared by devs(def=8)");
@@ -4210,7 +4272,8 @@ MODULE_PARM_DESC(guard, "protection checksum: 0=crc, 1=ip (def=0)");
 MODULE_PARM_DESC(host_lock, "host_lock is ignored (def=0)");
 MODULE_PARM_DESC(inq_vendor, "SCSI INQUIRY vendor string (def=\"Linux\")");
 MODULE_PARM_DESC(inq_product, "SCSI INQUIRY product string (def=\"scsi_debug\")");
-MODULE_PARM_DESC(inq_rev, "SCSI INQUIRY revision string (def=\"0186\")");
+MODULE_PARM_DESC(inq_rev, "SCSI INQUIRY revision string (def=\""
+		 SDEBUG_VERSION "\")");
 MODULE_PARM_DESC(lbpu, "enable LBP, support UNMAP command (def=0)");
 MODULE_PARM_DESC(lbpws, "enable LBP, support WRITE SAME(16) with UNMAP bit (def=0)");
 MODULE_PARM_DESC(lbpws10, "enable LBP, support WRITE SAME(10) with UNMAP bit (def=0)");
@@ -4884,6 +4947,24 @@ static ssize_t uuid_ctl_show(struct device_driver *ddp, char *buf)
 }
 static DRIVER_ATTR_RO(uuid_ctl);
 
+static ssize_t cdb_len_show(struct device_driver *ddp, char *buf)
+{
+	return scnprintf(buf, PAGE_SIZE, "%d\n", sdebug_cdb_len);
+}
+static ssize_t cdb_len_store(struct device_driver *ddp, const char *buf,
+			     size_t count)
+{
+	int ret, n;
+
+	ret = kstrtoint(buf, 0, &n);
+	if (ret)
+		return ret;
+	sdebug_cdb_len = n;
+	all_config_cdb_len();
+	return count;
+}
+static DRIVER_ATTR_RW(cdb_len);
+
 
 /* Note: The following array creates attribute files in the
    /sys/bus/pseudo/drivers/scsi_debug directory. The advantage of these
@@ -4923,6 +5004,7 @@ static struct attribute *sdebug_drv_attrs[] = {
 	&driver_attr_ndelay.attr,
 	&driver_attr_strict.attr,
 	&driver_attr_uuid_ctl.attr,
+	&driver_attr_cdb_len.attr,
 	NULL,
 };
 ATTRIBUTE_GROUPS(sdebug_drv);
-- 
2.14.1