Re: How are USB Rx interrupts periodically polled?
- Reply: Farhan Khan : "Re: How are USB Rx interrupts periodically polled?"
- In reply to: Farhan Khan : "How are USB Rx interrupts periodically polled?"
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Date: Fri, 06 May 2022 09:34:54 UTC
Hi Farhan, On 5/6/22 05:52, Farhan Khan wrote: > So, how is the polling of an Rx interrupt done? The software side typically queues a DMA job for the hardware. Every 125us the hardware wakes up and sends a packet to the device asking if it has data or not. If it has data, the DMA job completes, and a callback is generated for the USB stack. Then the received data is placed into the receive buffer for the USB transfer. This is is the same in OpenBSD and NetBSD, only that there they re-queue the USB transfer behind the scenes. Please beware that traditional USB is all polling based. Thunderbolt on the other side is different, and also the security aspects are different. --HPS