[SLOF] [PATCH 2/5] Stack optimization in libusb: split up setup_new_device()
Alexey Kardashevskiy
aik at ozlabs.ru
Mon Nov 30 17:01:15 AEDT 2015
On 11/26/2015 06:58 AM, Thomas Huth wrote:
> When scanning hubs, the code in libusb can be called recursively, for
> example usb_hub_init() calls setup_new_device(), which then calls
> slof_usb_handle() to execute Forth code for the next device.
> If that next device is a hub, we end up recursively in usb_hub_init()
> again.
> Since stack space is limited in SLOF, we can optimize here a little
> bit by splitting up the setup_new_device() function into the part
> that retrieves the descriptors (which takes most of the stack space
> in this code path since the descriptors are placed on the stack),
> and the part that populates the the device tree node of the new
> device (which is responsible for the recursion).
>
> Signed-off-by: Thomas Huth <thuth at redhat.com>
> ---
> lib/libusb/usb-core.c | 35 ++---------------------------------
> lib/libusb/usb-core.h | 7 +++++--
> lib/libusb/usb-ehci.c | 4 +++-
> lib/libusb/usb-hub.c | 4 +++-
> lib/libusb/usb-ohci.c | 4 +++-
> lib/libusb/usb-slof.c | 34 +++++++++++++++++++++++++++++++++-
> lib/libusb/usb-xhci.c | 4 +++-
> 7 files changed, 52 insertions(+), 40 deletions(-)
>
> diff --git a/lib/libusb/usb-core.c b/lib/libusb/usb-core.c
> index 6719c57..a55f016 100644
> --- a/lib/libusb/usb-core.c
> +++ b/lib/libusb/usb-core.c
> @@ -383,8 +383,6 @@ int usb_hid_exit(void *vdev)
> return true;
> }
>
> -#define usb_get_intf_class(x) ((x & 0x00FF0000) >> 16)
> -
> int usb_msc_init(void *vdev)
> {
> struct usb_dev *dev;
> @@ -420,7 +418,7 @@ int usb_msc_exit(void *vdev)
> return true;
> }
>
> -static int usb_msc_reset(struct usb_dev *dev)
> +int usb_msc_reset(struct usb_dev *dev)
> {
> struct usb_dev_req req;
>
> @@ -485,7 +483,7 @@ static int usb_handle_device(struct usb_dev *dev, struct usb_dev_config_descr *c
> return true;
> }
>
> -int setup_new_device(struct usb_dev *dev, unsigned int port)
> +int usb_setup_new_device(struct usb_dev *dev, unsigned int port)
> {
> struct usb_dev_descr descr;
> struct usb_dev_config_descr cfg;
Just to confirm - these descr/cfg plus the rest (ep/len/data) is what you
optimized by this patch (which is good, I am just making sure I read this
right)?
--
Alexey
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