Re: question on ehci's memory needs
Oliver Neukum <[email protected]>
| Newsgroups | gmane.linux.usb.devel |
|---|---|
| Message-ID | <[email protected]> |
Am Freitag, 29. Juni 2007 schrieb David Brownell: > On Friday 29 June 2007, Oliver Neukum wrote: > > Hi, > > > > I am trying to calculate worst cases memory requirements of EHCI. > > For bulk transfers it seems to me that you need size/16384 (rounded up) > > qtd and one qh. Is it really that easy? > > ISTR, yes. And interrupt transfers are the same. > > > What about the other transfer types? > > Control transfers are like bulk/intr, plus one more qtd. > > ISO is ISTR urb->number_of_packets plus a dummy qh. > What do you count? I am working on shifting all memory allocations to usb_alloc_urb(). Up to now I haven't required users of the API to specify the buffers at usb_alloc_urb() time, just a maximum length. Therefore I need the worst case. Regards Oliver ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ [email protected] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel