[SLOF] [PATCH 2/5] Stack optimization in libusb: split up setup_new_device()

[Alexey Kardashevskiy]

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