usb_gat_configuratio() used two pointers to point to the same
memory. Code simplified, by removing one of them.
Signed-off-by: Michal Nazarewicz <mina86@xxxxxxxxxx>
---
drivers/usb/core/config.c | 10 ++++------
1 files changed, 4 insertions(+), 6 deletions(-)
> On Sat, 17 Apr 2010, Michal Nazarewicz wrote:
>> usb_get_configuration() uses a temporary buffer allocated on heap
>> to read USB configuration descriptor. The buffer is just nine
>> bytes an so it is a waste to allocate it on heap where it can be
>> allocated on stack with the rest of local variables. This
>> simplifies the code and minimises memory usage.
Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> writes:
> This is completely wrong. You are not allowed to do DMA to buffers on
> the stack; some architectures are not capable of handling it.
That makes sense; I haven't considered this thinking that copying nine
bytes by CPU, rather then using DMA, is not a big issue.
Still, the change proposed by attached commit does not suffer from DMA
issue and still simplify the code.
diff --git a/drivers/usb/core/config.c b/drivers/usb/core/config.c
index 0d3af6a..4b23e7f 100644
--- a/drivers/usb/core/config.c
+++ b/drivers/usb/core/config.c
@@ -722,7 +722,6 @@ int usb_get_configuration(struct usb_device *dev)
int ncfg = dev->descriptor.bNumConfigurations;
int result = 0;
unsigned int cfgno, length;
- unsigned char *buffer;
unsigned char *bigbuffer;
struct usb_config_descriptor *desc;
@@ -751,17 +750,16 @@ int usb_get_configuration(struct usb_device *dev)
if (!dev->rawdescriptors)
goto err2;
- buffer = kmalloc(USB_DT_CONFIG_SIZE, GFP_KERNEL);
- if (!buffer)
+ desc = kmalloc(USB_DT_CONFIG_SIZE, GFP_KERNEL);
+ if (!desc)
goto err2;
- desc = (struct usb_config_descriptor *)buffer;
result = 0;
for (; cfgno < ncfg; cfgno++) {
/* We grab just the first descriptor so we know how long
* the whole configuration is */
result = usb_get_descriptor(dev, USB_DT_CONFIG, cfgno,
- buffer, USB_DT_CONFIG_SIZE);
+ desc, USB_DT_CONFIG_SIZE);
if (result < 0) {
dev_err(ddev, "unable to read config index %d "
"descriptor/%s: %d\n", cfgno, "start", result);
@@ -810,7 +808,7 @@ int usb_get_configuration(struct usb_device *dev)
result = 0;
err:
- kfree(buffer);
+ kfree(desc);
out_not_authorized:
dev->descriptor.bNumConfigurations = cfgno;
err2:
--
Best regards, _ _
.o. | Liege of Serenly Enlightened Majesty of o' \,=./ `o
..o | Computer Science, Michal "mina86" Nazarewicz (o o)
ooo +--<mina86-tlen.pl>--<jid:mina86-jabber.org>--ooO--(_)--Ooo--
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