commit 66dca2d97c69eb25710ffcefa7978ec5e44a5d27
author Josh Gao <jmgao@google.com> Thu Dec 17 13:45:18 2015 -0800
committer Josh Gao <jmgao@google.com> Thu Dec 17 14:28:24 2015 -0800
tree 590b80c454dca67cf9fc09fe2de1940834bd719f
parent 284d329480988029f433c4663906a5ce864c38a0

adb: extract USB FFS read/write limit constants.

Change-Id: I5e9fb7959a1c4744cb8d53ece4634138239d4e49

adb/usb_linux_client.cpp

diff --git a/adb/usb_linux_client.cpp b/adb/usb_linux_client.cpp
index 151c0aa..a4f1a70 100644
--- a/adb/usb_linux_client.cpp
+++ b/adb/usb_linux_client.cpp
@@ -30,6 +30,8 @@
 #include <sys/types.h>
 #include <unistd.h>
 
+#include <algorithm>
+
 #include "adb.h"
 #include "transport.h"
 
@@ -37,6 +39,13 @@
 #define MAX_PACKET_SIZE_HS	512
 #define MAX_PACKET_SIZE_SS	1024
 
+// Writes larger than 16k fail on some devices (seed with 3.10.49-g209ea2f in particular).
+#define USB_FFS_MAX_WRITE 16384
+
+// The kernel allocates a contiguous buffer for reads, which can fail for large ones due to
+// fragmentation. 16k chosen arbitrarily to match the write limit.
+#define USB_FFS_MAX_READ 16384
+
 #define cpu_to_le16(x)  htole16(x)
 #define cpu_to_le32(x)  htole32(x)
 
@@ -459,10 +468,9 @@
 static int usb_ffs_write(usb_handle* h, const void* data, int len) {
     D("about to write (fd=%d, len=%d)", h->bulk_in, len);
 
-    // Writes larger than 16k fail on some devices (seed with 3.10.49-g209ea2f in particular).
     const char* buf = static_cast<const char*>(data);
     while (len > 0) {
-        int write_len = (len > 16384) ? 16384 : len;
+        int write_len = std::min(USB_FFS_MAX_WRITE, len);
         int n = adb_write(h->bulk_in, buf, write_len);
         if (n < 0) {
             D("ERROR: fd = %d, n = %d: %s", h->bulk_in, n, strerror(errno));
@@ -481,7 +489,7 @@
 
     char* buf = static_cast<char*>(data);
     while (len > 0) {
-        int read_len = (len > 16384) ? 16384 : len;
+        int read_len = std::min(USB_FFS_MAX_READ, len);
         int n = adb_read(h->bulk_out, buf, read_len);
         if (n < 0) {
             D("ERROR: fd = %d, n = %d: %s", h->bulk_out, n, strerror(errno));