Re: [RFC] mass storage : emulation of sat scsi_pass_thru with ATACB

[matthieu castet <castet.matthieu-GANU6spQydw@public.gmane.org>]

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matthieu castet wrote:
> Hi,
> 
> I have got a cypress usb-ide bridge and I would like to tune or monitor
> my disk with tools like hdparm, hddtemp or smartctl.
> 
> My controller support a way to send raw ATA command to the disk with
> something call atacb (see
> http://download.cypress.com.edgesuite.net/design_resources/datasheets/contents/cy7c68300c_8.pdf). 
> 
> 
> First I start to add support for atacb in applications like smartctl.
> But there is some disadvantages :
> - I need to patch all application
> - A race is possible if there other accesses, because the emulation can
> be split in 2 atacb scsi transactions. One for sending the command, one
> for reading the register (if ck_cond is set).
> 
> So the idea to implement a SAT emulation for such device came to my mind.
> 
> First I want to ask, are there usb mass storage device that support SAT ?
> After some reading it seems impossible. Mass storage transparent scsi
> requires spc2 that only support fixed sense (starting with 0x70 or 0x71).
> But SAT need a sense with descriptor defined in spc3 (starting with 0x72
> or 0x73).
> 
> So SAT is not compatible with the sense format of mass storage ?
> 
> 
> 
> For doing the emulation, I want to provide a special proto_handler.
> 
> But I don't know what the best way to send command in my emulation layer :
> should I use usb_stor_invoke_transport or directly use us->transport.
> using usb_stor_invoke_transport save me lot's trouble of implementing
> error handling, but I can't control what I do.
> 
> What should I do if I got an error after sending the first command and
> ck_cond is set ? Should I still try to read the register ?
> 
> Is it safe to try to read the register if the first command did
> autosense ? Or should I only send the command, and read the register and
> compute the sense key, asc and ascq from registers ?
> 
> For the moment, my "draft" code look something like [1].
> 
> Any comments ?
> 
I attach a updated version of the driver.

I register the handler with an unsual entry. I don't know if it is the 
best way to do that (we need an entry for each device supporting atacb).

Another solution could have been to put the emulation in 
usb_stor_transparent_scsi_command, and if the device report invalidCDB 
don't try to use it again.

Any comments ?


Matthieu

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Index: linux-2.6.24.2/drivers/usb/storage/protocol.c
===================================================================
--- linux-2.6.24.2.orig/drivers/usb/storage/protocol.c	2008-02-29 22:14:09.000000000 +0100
+++ linux-2.6.24.2/drivers/usb/storage/protocol.c	2008-02-29 22:18:02.000000000 +0100
@@ -47,6 +47,8 @@
 #include <linux/highmem.h>
 #include <scsi/scsi.h>
 #include <scsi/scsi_cmnd.h>
+#include <scsi/scsi_eh.h>
+#include <linux/ata.h>
 
 #include "usb.h"
 #include "protocol.h"
@@ -144,6 +146,179 @@
 	usb_stor_invoke_transport(srb, us);
 }
 
+static void emulate_pass_thru_with_atacb(struct scsi_cmnd *srb,
+				       struct us_data *us)
+{
+	unsigned char save_cmnd[MAX_COMMAND_SIZE];
+	memcpy(save_cmnd, srb->cmnd, sizeof(save_cmnd));
+	memset(srb->cmnd, 0, sizeof(srb->cmnd));
+
+	/* check if we support the command */
+	if (save_cmnd[1] >> 5) /* MULTIPLE_COUNT */
+		goto invalid_fld;
+	/* check protocol */
+	switch((save_cmnd[1] >> 1) & 0xf) {
+		case 3:
+		case 4:
+		case 5:
+			break;
+		default:
+			goto invalid_fld;
+	}
+
+	/* first build the ATACB command */
+	srb->cmd_len = 16;
+
+	srb->cmnd[0] = 0x24; /* XXX this value can change */
+	srb->cmnd[1] = 0x24;
+	srb->cmnd[2] = 0;
+
+	srb->cmnd[3] = 0xff - 1;
+	srb->cmnd[4] = 1;
+
+	if (save_cmnd[0] == ATA_16) {
+		srb->cmnd[6] = save_cmnd[4]; /* features */
+		srb->cmnd[7] = save_cmnd[6]; /* sector count */
+		srb->cmnd[8] = save_cmnd[8]; /* lba low */
+		srb->cmnd[9] = save_cmnd[10]; /* lba med */
+		srb->cmnd[10] = save_cmnd[12]; /* lba high */
+		srb->cmnd[11] = save_cmnd[13]; /* device */
+		srb->cmnd[12] = save_cmnd[14]; /* command */
+
+		if (save_cmnd[1] & 0x01) {/* extended bit set */
+			if (save_cmnd[3] || save_cmnd[5] || save_cmnd[7] || save_cmnd[9]
+					|| save_cmnd[11])
+				goto invalid_fld;
+		}
+	}
+	else { /* ATA12 */
+		srb->cmnd[6] = save_cmnd[3]; /* features */
+		srb->cmnd[7] = save_cmnd[4]; /* sector count */
+		srb->cmnd[8] = save_cmnd[5]; /* lba low */
+		srb->cmnd[9] = save_cmnd[6]; /* lba med */
+		srb->cmnd[10] = save_cmnd[7]; /* lba high */
+		srb->cmnd[11] = save_cmnd[8]; /* device */
+		srb->cmnd[12] = save_cmnd[9]; /* command */
+
+	}
+	/* Filter SET_FEATURES - XFER MODE command */
+	if ((srb->cmnd[12] == ATA_CMD_SET_FEATURES)
+			&& (srb->cmnd[6] == SETFEATURES_XFER))
+		goto invalid_fld;
+
+	/* realy needed ? isd200 don't do that */
+	if (srb->cmnd[12] == ATA_CMD_ID_ATA || srb->cmnd[12] == ATA_CMD_ID_ATAPI)
+		srb->cmnd[2] |= (1<<7);
+
+
+	usb_stor_invoke_transport(srb, us);
+
+	/* if the device doesn't support ATACB
+	 * abort and register usb_stor_transparent_scsi_command
+	 * callback
+	 */
+	if (srb->result == SAM_STAT_CHECK_CONDITION &&
+			memcmp(srb->sense_buffer, usb_stor_sense_invalidCDB,
+				sizeof(usb_stor_sense_invalidCDB)) == 0) {
+		us->proto_handler = usb_stor_transparent_scsi_command;
+		goto end;
+	}
+
+	if ((srb->result != (DID_ERROR << 16) &&
+				srb->result != (DID_ABORT << 16)) &&
+			save_cmnd[2] & 0x20) { /* ck_cond */
+		/* read regs and put them in sense */
+		struct scsi_eh_save ses;
+		unsigned char sk, asc, ascq;
+		unsigned char regs[8];
+		unsigned char *sb = srb->sense_buffer;
+		unsigned char *desc = sb + 8;
+		int tmp_result;
+
+		if (srb->result == SAM_STAT_GOOD) {
+			/* OK */
+			sk = RECOVERED_ERROR;
+			asc = 0; /* ATA PASS THROUGH INFORMATION AVAILABLE */
+			ascq = 0x1D;
+		}
+		else {
+			/* save sense info */
+			/* XXX we get only 0, we should use regs status and error
+			 */
+#if 0
+			sk = sb[2];
+			asc = sb[12];
+			ascq = sb[13];
+#else
+			sk = ILLEGAL_REQUEST;
+			asc = 0x24;
+			ascq = 0;
+#endif
+		}
+
+
+		/* read registers */
+		srb->cmnd[2] = 1;
+		scsi_eh_prep_cmnd(srb, &ses, NULL, 0, 0);
+		srb->request_buffer = regs;
+		srb->request_bufflen = sizeof(regs);
+		srb->sc_data_direction = DMA_FROM_DEVICE;
+
+		usb_stor_invoke_transport(srb, us);
+		tmp_result = srb->result;
+		scsi_eh_restore_cmnd(srb, &ses);
+		/* we fail to get registers, report invalid command */
+		if (tmp_result != SAM_STAT_GOOD)
+			goto invalid_fld;
+
+		/* build the sense */
+		memset(sb, 0, sizeof(srb->sense_buffer));
+		/* XXX we should generate sk, asc, ascq from status and error
+		 * regs
+		 * (see 11.1 Error translation ­ ATA device error to SCSI error map)
+		 */
+		sb[1] = sk;
+		sb[2] = asc;
+		sb[3] = ascq;
+		sb[0] = 0x72;
+		desc[0] = 0x09; /* ATA_RETURN_DESCRIPTOR */
+
+		sb[7] = 14;
+		desc[1] = 12;
+
+		desc[2] = 0x00;
+		desc[3] = regs[1];
+		desc[5] = regs[2];
+		desc[7] = regs[3];
+		desc[9] = regs[4];
+		desc[11] = regs[5];
+		desc[12] = regs[6];
+		desc[13] = regs[7];
+
+		srb->result = (DRIVER_SENSE << 24) | SAM_STAT_CHECK_CONDITION;
+	}
+	goto end;
+invalid_fld:
+	srb->result = (DRIVER_SENSE << 24) | SAM_STAT_CHECK_CONDITION;
+
+	memcpy(srb->sense_buffer,
+			usb_stor_sense_invalidCDB,
+			sizeof(usb_stor_sense_invalidCDB));
+end:
+	memcpy(srb->cmnd, save_cmnd, sizeof(save_cmnd));
+	if (srb->cmnd[0] == ATA_12)
+		srb->cmd_len = 12;
+}
+
+void usb_stor_transparent_scsi_command_atacb(struct scsi_cmnd *srb,
+				       struct us_data *us)
+{
+	if (srb->cmnd[0] != ATA_16 && srb->cmnd[0] != ATA_12)
+		usb_stor_invoke_transport(srb, us);
+	else
+		emulate_pass_thru_with_atacb(srb, us);
+}
+
 /***********************************************************************
  * Scatter-gather transfer buffer access routines
  ***********************************************************************/
Index: linux-2.6.24.2/drivers/usb/storage/initializers.c
===================================================================
--- linux-2.6.24.2.orig/drivers/usb/storage/initializers.c	2008-02-29 22:14:09.000000000 +0100
+++ linux-2.6.24.2/drivers/usb/storage/initializers.c	2008-02-29 22:16:03.000000000 +0100
@@ -43,6 +43,7 @@
 #include "initializers.h"
 #include "debug.h"
 #include "transport.h"
+#include "protocol.h"
 
 /* This places the Shuttle/SCM USB<->SCSI bridge devices in multi-target
  * mode */
@@ -104,3 +105,13 @@
 	US_DEBUGP("usb_control_msg performing result is %d\n", result);
 	return (result ? 0 : -1);
 }
+
+/* This places register the atacb proto callback */
+int usb_atacb_init(struct us_data *us)
+{
+	/* XXX get atacb command from eeprom
+	 * ATM we assume the default : 0x24
+	 */
+	us->proto_handler = usb_stor_transparent_scsi_command_atacb;
+	return 0;
+}
Index: linux-2.6.24.2/drivers/usb/storage/initializers.h
===================================================================
--- linux-2.6.24.2.orig/drivers/usb/storage/initializers.h	2008-02-29 22:14:09.000000000 +0100
+++ linux-2.6.24.2/drivers/usb/storage/initializers.h	2008-02-29 22:16:03.000000000 +0100
@@ -50,3 +50,6 @@
 
 /* This places the HUAWEI E220 devices in multi-port mode */
 int usb_stor_huawei_e220_init(struct us_data *us);
+
+/* This places register the atacb proto callback */
+int usb_atacb_init(struct us_data *us);
Index: linux-2.6.24.2/drivers/usb/storage/protocol.h
===================================================================
--- linux-2.6.24.2.orig/drivers/usb/storage/protocol.h	2008-02-29 22:14:09.000000000 +0100
+++ linux-2.6.24.2/drivers/usb/storage/protocol.h	2008-02-29 22:16:03.000000000 +0100
@@ -47,6 +47,8 @@
 extern void usb_stor_ufi_command(struct scsi_cmnd*, struct us_data*);
 extern void usb_stor_transparent_scsi_command(struct scsi_cmnd*,
 		struct us_data*);
+extern void usb_stor_transparent_scsi_command_atacb(struct scsi_cmnd*,
+		struct us_data*);
 
 /* struct scsi_cmnd transfer buffer access utilities */
 enum xfer_buf_dir	{TO_XFER_BUF, FROM_XFER_BUF};
Index: linux-2.6.24.2/drivers/usb/storage/unusual_devs.h
===================================================================
--- linux-2.6.24.2.orig/drivers/usb/storage/unusual_devs.h	2008-02-29 22:14:09.000000000 +0100
+++ linux-2.6.24.2/drivers/usb/storage/unusual_devs.h	2008-02-29 22:16:03.000000000 +0100
@@ -1588,6 +1588,12 @@
 		US_SC_DEVICE, US_PR_DEVICE, NULL,
 		US_FL_CAPACITY_HEURISTICS),
 
+UNUSUAL_DEV(  0x04b4, 0x6830, 0x0000, 0x9999,
+		"Cypress",
+		"Cypress AT2LP",
+		US_SC_SCSI, US_PR_BULK, usb_atacb_init,
+		US_FL_NEED_OVERRIDE),
+
 /* Control/Bulk transport for all SubClass values */
 USUAL_DEV(US_SC_RBC, US_PR_CB, USB_US_TYPE_STOR),
 USUAL_DEV(US_SC_8020, US_PR_CB, USB_US_TYPE_STOR),