Re: [PATCH try#2] Blackfin ethernet driver: on chip ethernet MAC controller driver

[Robert Hancock <hancockr@shaw.ca>]

Bryan Wu wrote:
> On Sun, 2007-07-15 at 14:17 +0200, Michael Buesch wrote:
> > On Sunday 15 July 2007 14:07:44 Bryan Wu wrote:
> > > @@ -483,9 +487,12 @@
> > >  
> > >  void setup_mac_addr(u8 * mac_addr)
> > >  {
> > > +	u32 addr_low = le32_to_cpu(*(u32 *) & mac_addr[0]);
> > > +	u16 addr_hi = le16_to_cpu(*(u16 *) & mac_addr[4]);
> > > +
> > >  	/* this depends on a little-endian machine */
> > > -	bfin_write_EMAC_ADDRLO(*(u32 *) & mac_addr[0]);
> > > -	bfin_write_EMAC_ADDRHI(*(u16 *) & mac_addr[4]);
> > > +	bfin_write_EMAC_ADDRLO(addr_low);
> > > +	bfin_write_EMAC_ADDRHI(addr_hi);
> > >  }
> > >  
> > >  static void adjust_tx_list(void)
> > > @@ -866,10 +873,10 @@
> > >  	int retval;
> > >  
> > >  	/* Grab the MAC address in the MAC */
> > > -	*(u32 *) (&(dev->dev_addr[0])) = bfin_read_EMAC_ADDRLO();
> > > -	*(u16 *) (&(dev->dev_addr[4])) = (u16) bfin_read_EMAC_ADDRHI();
> > > +	*(u32 *) (&(dev->dev_addr[0])) = cpu_to_le32(bfin_read_EMAC_ADDRLO());
> > > +	*(u16 *) (&(dev->dev_addr[4])) = cpu_to_le16((u16) bfin_read_EMAC_ADDRHI());
> > Try something like this:
> >
> > @@ -483,9 +487,12 @@
> >  
> >  void setup_mac_addr(u8 * mac_addr)
> >  {
> > +       u32 addr_low = le32_to_cpu(*(__le32 *) & mac_addr[0]);
> > +       u16 addr_hi = le16_to_cpu(*(__le16 *) & mac_addr[4]);
> > +
> > -       /* this depends on a little-endian machine */
> > -       bfin_write_EMAC_ADDRLO(*(u32 *) & mac_addr[0]);
> > -       bfin_write_EMAC_ADDRHI(*(u16 *) & mac_addr[4]);
> > +       bfin_write_EMAC_ADDRLO(addr_low);
> > +       bfin_write_EMAC_ADDRHI(addr_hi);
> >  }
> >  
> >  static void adjust_tx_list(void)
> > @@ -866,10 +873,10 @@
> >         int retval;
> >  
> >         /* Grab the MAC address in the MAC */
> > -       *(u32 *) (&(dev->dev_addr[0])) = bfin_read_EMAC_ADDRLO();
> > -       *(u16 *) (&(dev->dev_addr[4])) = (u16) bfin_read_EMAC_ADDRHI();
> > +       *(__le32 *) (&(dev->dev_addr[0])) = cpu_to_le32(bfin_read_EMAC_ADDRLO());
> > +       *(__le16 *) (&(dev->dev_addr[4])) = cpu_to_le16((u16) bfin_read_EMAC_ADDRHI());
>
> Thanks a lot, Michael. 
>
> I got a generic question about this endianess check. When should use it
> in a driver or something else? I grep it in the driver/net/
>
> ---
> drivers/net/e100.c:             ns->tx_window_errors += le32_to_cpu(s->tx_late_collisions);
> drivers/net/e100.c:             ns->tx_carrier_errors += le32_to_cpu(s->tx_lost_crs);
> drivers/net/e100.c:             ns->tx_fifo_errors += le32_to_cpu(s->tx_underruns);
> drivers/net/e100.c:             ns->tx_errors += le32_to_cpu(s->tx_max_collisions) +
> drivers/net/e100.c:                     le32_to_cpu(s->tx_lost_crs);
> drivers/net/e100.c:             ns->rx_length_errors += le32_to_cpu(s->rx_short_frame_errors) +
> drivers/net/e100.c:             ns->rx_crc_errors += le32_to_cpu(s->rx_crc_errors);
> drivers/net/e100.c:             ns->rx_frame_errors += le32_to_cpu(s->rx_alignment_errors);
> drivers/net/e100.c:             ns->rx_over_errors += le32_to_cpu(s->rx_overrun_errors);
> drivers/net/e100.c:             ns->rx_fifo_errors += le32_to_cpu(s->rx_overrun_errors);
> drivers/net/e100.c:             ns->rx_missed_errors += le32_to_cpu(s->rx_resource_errors);
> drivers/net/e100.c:             ns->rx_errors += le32_to_cpu(s->rx_crc_errors) +
> drivers/net/e100.c:                     le32_to_cpu(s->rx_alignment_errors) +
> drivers/net/e100.c:                     le32_to_cpu(s->rx_short_frame_errors) +
> drivers/net/e100.c:                     le32_to_cpu(s->rx_cdt_errors);
> drivers/net/e100.c:             nic->tx_deferred += le32_to_cpu(s->tx_deferred);
> drivers/net/e100.c:                     le32_to_cpu(s->tx_single_collisions);
> drivers/net/e100.c:                     le32_to_cpu(s->tx_multiple_collisions);
> drivers/net/e100.c:                     nic->tx_fc_pause += le32_to_cpu(s->fc_xmt_pause);
> drivers/net/e100.c:                     nic->rx_fc_pause += le32_to_cpu(s->fc_rcv_pause);
> drivers/net/e100.c:                             le32_to_cpu(s->fc_rcv_unsupported);
> drivers/net/e100.c:                             le32_to_cpu(cb->u.tcb.tbd.buf_addr),
> drivers/net/e100.c:                                     le32_to_cpu(cb->u.tcb.tbd.buf_addr),
> ---
>
> Normally, it is used to protect some rx/tx status flags or dma buf addr.
>
> Any guide line for this leXX_to_cpu usage?

It has to be used when accessing any data structure stored in RAM that 
the device will access and where byte order is significant. cpu_to_le32 
when writing to the RAM, le32_to_cpu when reading it. (or le16, etc. if 
needed).

--
Robert Hancock      Saskatoon, SK, Canada
To email, remove "nospam" from hancockr@nospamshaw.ca
Home Page: http://www.roberthancock.com/

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