Hi , hiddev ring buffer size ( HIDDEV_BUFFER_SIZE ) as defined in driver/hid/usbhid/hiddev.c is 2048 bytes . similarly hidraw ring buffer size (HIDRAW_BUFFER_SIZE) as defined in include/linux/hidraw.h is 64 bytes . i am presently using both hiddev and hidraw driver with a USB HID device ( ipod ). My queries are as follows : 1) How was it calculated that hiddev ring buffer size of 2048 bytes is sufficient to handle usb hid report traffic coming from a usb high speed device exposing HID interface ? Similarly how the value of HIDRAW_BUFFER_SIZE was calculated for a USBHID high speed device ? . While computing such ring buffer size values , what all factors/loads should be taken into account ? 2) Are these current values of HIDDEV_BUFFER_SIZE , HIDRAW_BUFFER_SIZE optimum enough to handle any USB HID high speed device present currently ? 3) What max latency ( in ms ? or us ? ) application can have between 2 consecutive reads() over USBHID interface , so that these ring buffers donot overflow in any situations ? 4) i observed that the value of HIDDEV_BUFFER_SIZE was 64 bytes till 2.6.31 kernel , and in 2.6.32 kernel HIDDEV_BUFFER_SIZE was increased to 2048 bytes to handle reports from full speed and high speed USB hid devices with the patch at http://kerneltrap.org/mailarchive/git-commits-head/2009/9/15/5178 . Will these values needs to be increased again in future keeping in view Superspeed usb3.0 ? Thanx & Regards Amit Nagal -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
