Hi all, I was wondering if there was a way to notify userspace readers about _how much_ data was to be read, not just readiness for a read or write? poll(2)/select(2) just let the userspace processes know about whether or not an operation will block, it would seem. The problem at hand is that the data being buffered in my driver is of different sizes (therefore its a character driver, not a block driver), but the units are stored in a list where a read request will return 1 or more of the units atomically (meaning that the whole unit is read or not). For example, if there are 5 units in the list of sizes 1000, 2000, 4000, 2000 and 6000 bytes, the process should be notified that there are 15,000 bytes of data available to be read. Should the process specify a count of 8192 bytes, for example, the driver could then only write the first three units of memory. Does anyone know of a way to let the userspace processes know how much data is in my driver's buffer in advance of a read(2) so that it can avoid blocking and also exhibit the maximum transfer rate from kernel to userspace? Thanks in advance! :) -- [ Tobias DiPasquale ] 0x636f6465736c696e67657240676d61696c2e636f6d - : send the line "unsubscribe linux-net" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
