From: Kevin Grant <redacted>
Date: Fri, 1 Oct 2021 17:04:08 +0000 (+0100)
Subject: kingst-la2016: setup usb transfer sizes to be multiple of endpoint max packet size... 
X-Git-Url: https://sigrok.org/gitweb/?p=libsigrok.git;a=commitdiff_plain;h=e847645b7be832c1d62d1ad2312e3a3d4de467ce

kingst-la2016: setup usb transfer sizes to be multiple of endpoint max packet size, as required by WinUSB RAW_IO policy
---

diff --git a/src/hardware/kingst-la2016/api.c b/src/hardware/kingst-la2016/api.c
index 9ab2e564..1b1b425a 100644
--- a/src/hardware/kingst-la2016/api.c
+++ b/src/hardware/kingst-la2016/api.c
@@ -641,8 +641,11 @@ static void LIBUSB_CALL receive_transfer(struct libusb_transfer *transfer)
 	devc->n_bytes_to_read -= transfer->actual_length;
 	if (devc->n_bytes_to_read) {
 		uint32_t to_read = devc->n_bytes_to_read;
-		if (to_read > LA2016_BULK_MAX)
-			to_read = LA2016_BULK_MAX;
+		/* determine read size for the next usb transfer */
+		if (to_read >= LA2016_USB_BUFSZ)
+			to_read = LA2016_USB_BUFSZ;
+		else /* last transfer, make read size some multiple of LA2016_EP6_PKTSZ */
+			to_read = (to_read + (LA2016_EP6_PKTSZ-1)) & ~(LA2016_EP6_PKTSZ-1);
 		libusb_fill_bulk_transfer(
 			transfer, usb->devhdl,
 			0x86, transfer->buffer, to_read,
diff --git a/src/hardware/kingst-la2016/protocol.c b/src/hardware/kingst-la2016/protocol.c
index 22d94411..ecb21e3f 100644
--- a/src/hardware/kingst-la2016/protocol.c
+++ b/src/hardware/kingst-la2016/protocol.c
@@ -723,9 +723,11 @@ SR_PRIV int la2016_start_retrieval(const struct sr_dev_inst *sdi, libusb_transfe
 	}
 
 	to_read = devc->n_bytes_to_read;
-	if (to_read > LA2016_BULK_MAX)
-		to_read = LA2016_BULK_MAX;
-
+	/* choose a buffer size for all of the usb transfers */
+	if (to_read >= LA2016_USB_BUFSZ)
+		to_read = LA2016_USB_BUFSZ; /* multiple transfers */
+	else /* one transfer, make buffer size some multiple of LA2016_EP6_PKTSZ */
+		to_read = (to_read + (LA2016_EP6_PKTSZ-1)) & ~(LA2016_EP6_PKTSZ-1);
 	buffer = g_try_malloc(to_read);
 	if (!buffer) {
 		sr_err("Failed to allocate %d bytes for bulk transfer", to_read);
diff --git a/src/hardware/kingst-la2016/protocol.h b/src/hardware/kingst-la2016/protocol.h
index 58998b24..09e12be6 100644
--- a/src/hardware/kingst-la2016/protocol.h
+++ b/src/hardware/kingst-la2016/protocol.h
@@ -37,6 +37,16 @@
 
 #define LA2016_BULK_MAX         8388608
 
+/*
+ * On Windows sigrok uses WinUSB RAW_IO policy which requires the
+ * USB transfer buffer size to be a multiple of the endpoint max packet
+ * size, which is 512 bytes in this case. Also, the maximum allowed size of
+ * the transfer buffer is normally read from WinUSB_GetPipePolicy API but
+ * libusb does not expose this function. Typically, max size is 2MB.
+ */
+#define LA2016_EP6_PKTSZ	512 /* endpoint 6 max packet size */
+#define LA2016_USB_BUFSZ	(256 * 2 * LA2016_EP6_PKTSZ) /* 256KB buffer */
+
 #define MAX_RENUM_DELAY_MS	3000
 #define DEFAULT_TIMEOUT_MS      200