On Mon, Aug 09, 2021 at 10:15:29AM +0200, Oliver Neukum wrote:
On 09.08.21 09:58, Muni Sekhar wrote:
Hi all,
PCIe memory mapped registers can be read via readb(), readw(), readl() kernel API's. Similarly what are the kernel API to read the device registers via USB bus
Hi,
I am afraid this is based on a fundamental misunderstanding on how USB works. It is based on passing messages, not reading and writing registers.
USB devices are primarily based on endpoints, not registers. A literal answer to your question would point you to the clear/set/get_feature standard requests of chapter 9 of the specification, but that really will not help you, as you are making assumption that fundamentally do not apply.
I hope this list stays friendly to newcomers and we will answer specific questions, but at this point I must advise you to first read an introductory book.
Along these lines, take a look at the book, Linux Device Drivers, third edition, which is free online, as it has a chapter about USB drivers and how they work. That should help you out to understand the issues involved with USB devices. If you have specific questions after looking at that, and reading the basic usb-skeleton.c driver in the kernel source tree, please let us know! thanks, greg k-h