Re: USB Hid driver Help

[Greg KH <greg@kroah.com>]

On Mon, Feb 03, 2020 at 04:32:46PM +0000, Lucas Tanure wrote:
> Hi,
> 
> I'm trying to write a Hid driver for MCP2210.

What type of device is this?

> But the USB Hid specification is quite complicated.

The kernel should do it "all for you" already, why do you need to create
a custom HID driver for this device?

What type of HID reports does the device export and why doesn't the
existing kernel drivers work for you?

> I would like to know how to send and receive data to the device. Any
> links to a good tutorial ?

HID has the idea of "reports" and data comes in and out in that specific
format, all depending on how the device describes itself.  There's isn't
usually a normal "send/receive" type of thing, but it all depends on the
type of device.

> This is my current driver is attached.
> 
> Thanks
> Lucas

> #define DEBUG
> #include <linux/module.h>
> #include <linux/hid.h>
> #include <linux/usb.h>
> 
> static int mcp2210_probe(struct hid_device *hdev,
> 			 const struct hid_device_id *id)
> {
> 	struct usb_interface *intf = to_usb_interface(hdev->dev.parent);
> 	int ret = 0;
> 
> 	hid_dbg(hdev, "%s\n", __FUNCTION__);
> 
> 	ret = hid_parse(hdev);
> 	if (ret) {
> 		hid_err(hdev, "parse failed\n");
> 		return ret;
> 	} else {
> 		hid_dbg(hdev, "parse success\n");
> 	}
> 
> 	ret = hid_hw_start(hdev, HID_CONNECT_DEFAULT);
> 	if (ret) {
> 		hid_err(hdev, "hw start failed\n");
> 		return ret;
> 	} else {
> 		hid_dbg(hdev, "start success\n");
> 	}

Does this all work?

What fails?

thanks,

greg k-h

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