[PATCH v3] gpib: agilent_82357a: Support some 82357B clones

[Tom Keller <tom@tompkel.net>]

Some adapters marked as Agilent/Keysight 82357B are clones that contain
their own firmware. They do not support XFER_STATUS and need slightly
relaxed timing. Detect clone adapters that fail a firmware load and work
around their quirks.

Signed-off-by: Tom Keller <tom@tompkel.net>
---
Changes since v2:
- Use 819 ns as the default FAST_TALKER_T1 for all adapters and drop
  the clone-specific initialization.
- Reword the clone detection message.
Changes since v1:
- Keep the existing init sequence, add a small increase to FAST_TALKER_T1
  on clones.
- Clear AWF_NO_FAST_TALKER_FIRST_BYTE on command writes for all
  adapters.
v2: https://lore.kernel.org/all/20260902224109.2130225-1-tom@tompkel.net/
v1: https://lore.kernel.org/all/20260901233621.1823280-1-tom@tompkel.net/
 drivers/gpib/agilent_82357a/agilent_82357a.c | 41 +++++++++++++++++++-
 drivers/gpib/agilent_82357a/agilent_82357a.h |  2 +
 2 files changed, 41 insertions(+), 2 deletions(-)

diff --git a/drivers/gpib/agilent_82357a/agilent_82357a.c b/drivers/gpib/agilent_82357a/agilent_82357a.c
index 2468a471d1755..5b34fe7e13662 100644
--- a/drivers/gpib/agilent_82357a/agilent_82357a.c
+++ b/drivers/gpib/agilent_82357a/agilent_82357a.c
@@ -567,7 +567,7 @@ static ssize_t agilent_82357a_generic_write(struct gpib_board *board,
 	out_data[i++] = 0; // secondary address when AWF_NO_ADDRESS is not set
 	out_data[i] = AWF_NO_ADDRESS | AWF_NO_FAST_TALKER_FIRST_BYTE;
 	if (send_commands)
-		out_data[i] |= AWF_ATN | AWF_NO_FAST_TALKER;
+		out_data[i] = AWF_ATN | AWF_NO_ADDRESS | AWF_NO_FAST_TALKER;
 	if (send_eoi)
 		out_data[i] |= AWF_SEND_EOI;
 	++i;
@@ -652,6 +652,16 @@ static ssize_t agilent_82357a_generic_write(struct gpib_board *board,
 		return -ETIMEDOUT;
 	}
 
+	/*
+	 * Clone adapters do not answer to XFER_STATUS, so use the
+	 * bytes_written from the write complete interrupt.
+	 */
+	if (a_priv->is_clone_82357b) {
+		mutex_unlock(&a_priv->bulk_transfer_lock);
+		*bytes_written = a_priv->write_complete_count;
+		return 0;
+	}
+
 	status_data = kmalloc(STATUS_DATA_LEN, GFP_KERNEL);
 	if (!status_data) {
 		mutex_unlock(&a_priv->bulk_transfer_lock);
@@ -1114,6 +1124,12 @@ static void agilent_82357a_interrupt_complete(struct urb *urb)
 	}
 
 	interrupt_flags = transfer_buffer[0];
+	if (urb->actual_length >= 6 && test_bit(AIF_WRITE_COMPLETE_BN, &interrupt_flags)) {
+		a_priv->write_complete_count  = (u32)transfer_buffer[2];
+		a_priv->write_complete_count |= (u32)transfer_buffer[3] << 8;
+		a_priv->write_complete_count |= (u32)transfer_buffer[4] << 16;
+		a_priv->write_complete_count |= (u32)transfer_buffer[5] << 24;
+	}
 	if (test_bit(AIF_READ_COMPLETE_BN, &interrupt_flags))
 		set_bit(AIF_READ_COMPLETE_BN, &a_priv->interrupt_flags);
 	if (test_bit(AIF_WRITE_COMPLETE_BN, &interrupt_flags))
@@ -1213,6 +1229,26 @@ static void agilent_82357a_free_private(struct gpib_board *board)
 	board->private_data = NULL;
 }
 
+static void agilent_82357a_detect_clone(struct agilent_82357a_priv *a_priv)
+{
+	struct usb_device *usb_dev = interface_to_usbdev(a_priv->bus_interface);
+	u8 *ret_data;
+	int retval;
+
+	ret_data = kmalloc(1, GFP_KERNEL);
+	if (!ret_data)
+		return;
+	retval = usb_control_msg(usb_dev, usb_rcvctrlpipe(usb_dev, 0), 0xA0,
+				 USB_DIR_IN | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
+				 0xE600, 0, ret_data, 1, 100);
+	kfree(ret_data);
+	if (retval < 0) {
+		a_priv->is_clone_82357b = 1;
+		dev_info(&usb_dev->dev, "82357B clone with firmware detected (CPUCS read returned %i)\n",
+			 retval);
+	}
+}
+
 #define INIT_NUM_REG_WRITES 18
 static int agilent_82357a_init(struct gpib_board *board)
 {
@@ -1346,6 +1382,7 @@ static int agilent_82357a_attach(struct gpib_board *board, const struct gpib_boa
 	case USB_DEVICE_ID_AGILENT_82357B:
 		a_priv->bulk_out_endpoint = AGILENT_82357B_BULK_OUT_ENDPOINT;
 		a_priv->interrupt_in_endpoint = AGILENT_82357B_INTERRUPT_IN_ENDPOINT;
+		agilent_82357a_detect_clone(a_priv);
 		break;
 	default:
 		dev_err(&usb_dev->dev, "bug, unhandled product_id in switch?\n");
@@ -1359,7 +1396,7 @@ static int agilent_82357a_attach(struct gpib_board *board, const struct gpib_boa
 
 	timer_setup(&a_priv->bulk_timer, agilent_82357a_timeout_handler, 0);
 
-	board->t1_nano_sec = 800;
+	board->t1_nano_sec = 819;
 
 	retval = agilent_82357a_init(board);
 
diff --git a/drivers/gpib/agilent_82357a/agilent_82357a.h b/drivers/gpib/agilent_82357a/agilent_82357a.h
index 33ac558e55528..2013163446965 100644
--- a/drivers/gpib/agilent_82357a/agilent_82357a.h
+++ b/drivers/gpib/agilent_82357a/agilent_82357a.h
@@ -133,12 +133,14 @@ struct agilent_82357a_priv {
 	struct mutex bulk_alloc_lock;		// bulk transfer allocation lock
 	struct mutex interrupt_alloc_lock;	// interrupt allocation lock
 	struct mutex control_alloc_lock;	// control message allocation lock
+	u32 write_complete_count;               // bytes transferred in last write
 	struct timer_list bulk_timer;
 	struct agilent_82357a_urb_ctx context;
 	unsigned int bulk_out_endpoint;
 	unsigned int interrupt_in_endpoint;
 	unsigned is_cic : 1;
 	unsigned ren_state : 1;
+	unsigned is_clone_82357b : 1;
 };
 
 struct agilent_82357a_register_pairlet {
-- 
2.55.0