Re: [PATCH] Topcliff PHUB: Generate PacketHub driver

["Masayuki Ohtake" <masa-korg@dsn.okisemi.com>]

Hi Arnd,

I will modify for your comments by today or tomorrow.

Thanks,
Ohtake

----- Original Message ----- 
From: "Arnd Bergmann" <arnd@arndb.de>
To: "Masayuki Ohtak" <masa-korg@dsn.okisemi.com>
Cc: "Alan Cox" <alan@lxorguk.ukuu.org.uk>; "LKML" <linux-kernel@vger.kernel.org>; "Andrew"
<andrew.chih.howe.khor@intel.com>; "Intel OTC" <joel.clark@intel.com>; "Wang, Qi" <qi.wang@intel.com>; "Wang, Yong Y"
<yong.y.wang@intel.com>
Sent: Thursday, June 17, 2010 8:59 PM
Subject: Re: [PATCH] Topcliff PHUB: Generate PacketHub driver


> Looks almost good to me now. Some more details (only the -EFAULT return code
> is a real issue, the other ones are cosmetic changes):
>
> On Thursday 17 June 2010, Masayuki Ohtak wrote:
> > +
> > +#define PCH_READ_REG(a) ioread32(pch_phub_reg.pch_phub_base_address + (a))
> > +
> > +#define PCH_WRITE_REG(a, b) iowrite32((a), pch_phub_reg.pch_phub_base_address +\
> > + (b))
>
> I'd recommend just getting rid of these abstractions. You only use
> them in one or two functions each, so you can just as well add a local
> variable there and do
>
> void __iomem *p = pch_phub_reg.pch_phub_base_address;
> foo = ioread32(p + foo_offset);
> bar = ioread32(p + bar_offset);
> ...
>
> Not really important, but this way it would be more conventional
> without having to write extra code.
>
> > +/*--------------------------------------------
> > + global variables
> > +--------------------------------------------*/
> > +/**
> > + * struct pch_phub_reg_t - PHUB register structure
> > + * @phub_id_reg: PHUB_ID register val
> > + * @q_pri_val_reg: QUEUE_PRI_VAL register val
> > + * @rc_q_maxsize_reg: RC_QUEUE_MAXSIZE register val
> > + * @bri_q_maxsize_reg: BRI_QUEUE_MAXSIZE register val
> > + * @comp_resp_timeout_reg: COMP_RESP_TIMEOUT register val
> > + * @bus_slave_control_reg: BUS_SLAVE_CONTROL_REG register val
> > + * @deadlock_avoid_type_reg:  DEADLOCK_AVOID_TYPE register val
> > + * @intpin_reg_wpermit_reg0:  INTPIN_REG_WPERMIT register 0 val
> > + * @intpin_reg_wpermit_reg1:  INTPIN_REG_WPERMIT register 1 val
> > + * @intpin_reg_wpermit_reg2:  INTPIN_REG_WPERMIT register 2 val
> > + * @intpin_reg_wpermit_reg3:  INTPIN_REG_WPERMIT register 3 val
> > + * @int_reduce_control_reg: INT_REDUCE_CONTROL registers val
> > + * @clkcfg_reg: CLK CFG register val
> > + * @pch_phub_base_address:  register base address
> > + * @pch_phub_extrom_base_address:  external rom base address
> > + * @pch_phub_suspended: PHUB status val
> > + */
> > +struct pch_phub_reg_t {
>
> It would be better to drop the _t postfix on the type name.
> By convention, we use this only for typedefs on simple data
> types like off_t but not for structures.
>
> > + __u32 phub_id_reg;
> > + __u32 q_pri_val_reg;
> > + __u32 rc_q_maxsize_reg;
>
> When I told you to change the ioctl arguments to use __u32 instead
> of u32, I was only referring to those parts that are in the user-visible
> section of the header file. While it does not hurt to use __u32 in
> the kernel, you should understand the distinction.
>
> > +/** pch_phub_write - Implements the write functionality of the Packet Hub
> > + *  module.
> > + *  @file: Contains the reference of the file structure
> > + *  @buf: Usermode buffer pointer
> > + *  @size: Usermode buffer size
> > + *  @ppos: Contains the reference of the file structure
> > + */
> > +static ssize_t pch_phub_write(struct file *file, const char __user *buf,
> > + size_t size, loff_t *ppos)
> > +{
> > + static __u32 data;
>
> No need to make data static.
>
> > + __s32 ret_value;
> > + __u32 addr_offset = 0;
> > + loff_t pos = *ppos;
> > +
> > + if (pos < 0)
> > + return -EINVAL;
> > +
> > + for (addr_offset = 0; addr_offset < size; addr_offset++) {
> > + get_user(data, &buf[addr_offset]);
> > +
> > + ret_value = pch_phub_write_serial_rom(0x80 + addr_offset + pos,
> > + data);
> > + if (ret_value)
> > + return -EFAULT;
>
> You should return -EFAULT if the get_user() call fails, otherwise you have
> a possible security hole. If pch_phub_write_serial_rom fails, the correct
> return code would be -EIO.
>
> > +/**
> > + * file_operations structure initialization
> > + */
> > +static const struct file_operations pch_phub_fops = {
> > + .owner = THIS_MODULE,
> > + .read = pch_phub_read,
> > + .write = pch_phub_write,
> > + .unlocked_ioctl = pch_phub_ioctl,
> > +};
>
> If would be good to add a line of
> .llseek = default_llseek,
> here. I have a patch to change the default llseek method to one
> that disallows seeking, so if you add this line, there is one
> less driver for me to patch.
>
> Arnd
>