Re: [PATCH 1/7] char/mei: PCI device and char driver support.

From: Arnd Bergmann
Date: Tue Mar 22 2011 - 13:23:01 EST

On Tuesday 22 March 2011, Oren Weil wrote:
> +static ssize_t mei_read(struct file *file, char __user *ubuf,
> + size_t length, loff_t *offset)
> +{
> + int i;
> + int rets;
> + int err;
> + int if_num = iminor(file->f_dentry->d_inode);
> + struct mei_file_private *file_ext = file->private_data;
> + struct mei_cb_private *priv_cb_pos = NULL;
> + struct mei_cb_private *priv_cb = NULL;
> + struct mei_device *dev;
> +
> + if (!mei_device)
> + return -ENODEV;
> +
> + dev = pci_get_drvdata(mei_device);
> + if (if_num != MEI_MINOR_NUMBER || !dev || !file_ext)
> + return -ENODEV;
> +

I'm very confused by this code and how you support multiple
instances of PCI devices, cb_list entries and concurrent connections:

* You look up a global pointer to mei_device, when there could
be multiple PCI devices.

* You use the minor number of the chardev as an index throughout
the code, but bail out if it does not match a constant.

* You walk a list of mei_cb_private entries when you should have
just a single one for this file. In other places, you walk a list
of mei_file_private entries.

I think you should try to document your data structures and how
they relate to each other, and remove all that turn out not to
be needed in the process.

>From the brief look I had at this rather complex code, I would
assume that it could look something like this:

* In the PCI probe function, create a misc character device for
every instance you find behind each device. Remove the global
variables and constants.

* Unify mei_file_private and mei_cb_private, allocate at open
time but fill when the ioctl gets called.

Would that work, or am I missing something major?

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