Hi Greg, On Wed, Apr 29, 2020 at 09:20:36AM +0200, Greg KH wrote: > On Wed, Apr 29, 2020 at 01:26:50AM +0530, mani@xxxxxxxxxx wrote: > > From: Manivannan Sadhasivam <mani@xxxxxxxxxx> > > > > Add support for MaxLinear/Exar USB to Serial converters. This driver > > only supports XR21V141X series but provision has been made to support > > other series in future. > > > > This driver is inspired from the initial one submitted by Patong Yang: > > > > https://patchwork.kernel.org/patch/10543261/ > > > > While the initial driver was a custom tty USB driver exposing whole > > new serial interface ttyXRUSBn, this version is completely based on USB > > serial core thus exposing the interfaces as ttyUSBn. This will avoid > > the overhead of exposing a new USB serial interface which the userspace > > tools are unaware of. > > Nice work! > > Some comments below: > > > +// SPDX-License-Identifier: GPL-2.0+ > > +/* > > + * MaxLinear/Exar USB to Serial driver > > + * > > + * Based on initial driver written by Patong Yang <patong.mxl@xxxxxxxxx> > > + * > > + * Copyright (c) 2020 Manivannan Sadhasivam <mani@xxxxxxxxxx> > > + */ > > + > > +#include <linux/kernel.h> > > +#include <linux/module.h> > > +#include <linux/slab.h> > > +#include <linux/tty.h> > > +#include <linux/usb.h> > > +#include <linux/usb/serial.h> > > + > > +#include "xr_serial.h" > > No need for a .h file for a single .c file. > Yeah but since this driver can support multiple series of XR chips (they might have separate register definitions and such), I thought it is a good idea to have a header file to keep the driver sane. But can club it to the source file for now. > > +static int xr_get_reg(struct usb_serial_port *port, u8 block, u16 reg, > > + u16 *val) > > +{ > > + struct usb_serial *serial = port->serial; > > + struct xr_port_private *port_priv = usb_get_serial_port_data(port); > > + void *dmabuf; > > + int ret = -EINVAL; > > + > > + dmabuf = kmalloc(sizeof(reg), GFP_KERNEL); > > So that is 2 bytes? > Explanation below... > > + if (!dmabuf) > > + return -ENOMEM; > > + > > + if (port_priv->idProduct == XR21V141X_ID) { > > + /* XR21V141X uses custom command for reading UART registers */ > > + ret = usb_control_msg(serial->dev, > > + usb_rcvctrlpipe(serial->dev, 0), > > + XR_GET_XR21V141X, > > + USB_DIR_IN | USB_TYPE_VENDOR, 0, > > + reg | (block << 8), dmabuf, > > + port_priv->reg_width, > > + USB_CTRL_SET_TIMEOUT); > > + } > > + > > + if (ret == port_priv->reg_width) { > > + memcpy(val, dmabuf, port_priv->reg_width); > > But here you copy ->reg_width bytes in? How do you know val can hold > that much? It's only set to be 1, so you copy 1 byte to a 16bit value? > What part of the 16bits did you just copy those 8 bits to (hint, think > cpu endian issues...) > > That feels really really odd and a bit broken. > Right. The reason is, the other series which can be supported by this driver have different register widths. For instance XR2280x. I haven't used them personally but seen this in initial driver. So I just used the max u16 type to make the reg_{set/get} routines work with those. But agree, I should've used le16_to_cpu() cast to avoid endian issues. If you think this hack is not required now, I can just use u8 and worry about compatibility later. > > --- /dev/null > > +++ b/drivers/usb/serial/xr_serial.h > > @@ -0,0 +1,103 @@ > > +/* SPDX-License-Identifier: GPL-2.0+ */ > > Are you sure about the "+"? I have to ask :) > I'm not a fan but since I've inherited the code from initial driver (which was GPL-2.0+), I kept it. > > + > > +#ifndef __LINUX_USB_SERIAL_XR_SERIAL_H > > +#define __LINUX_USB_SERIAL_XR_SERIAL_H > > As you will drop this file, just a general statement, no need for > __LINUX as this is all Linux :) > Sure. Thanks, Mani > thanks, > > greg k-h
