linux-kernel - Re: [PATCH 1/2] device property: Add device_get_bd_address() and fwnode_get_bd

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Date:   Fri, 21 Sep 2018 09:40:58 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Sakari Ailus <sakari.ailus@...ux.intel.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Marcin Wojtas <mw@...ihalf.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Sinan Kaya <okaya@...eaurora.org>,
        Marcel Holtmann <marcel@...tmann.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        linux-kernel@...r.kernel.org, linux-bluetooth@...r.kernel.org,
        Balakrishna Godavarthi <bgodavar@...eaurora.org>,
        Loic Poulain <loic.poulain@...aro.org>,
        Brian Norris <briannorris@...omium.org>
Subject: Re: [PATCH 1/2] device property: Add device_get_bd_address() and
 fwnode_get_bd_address()

Hi Sakari,

On Fri, Sep 21, 2018 at 10:13:12AM +0300, Sakari Ailus wrote:
> Hi Matthias,
> 
> On Thu, Sep 20, 2018 at 03:34:35PM -0700, Matthias Kaehlcke wrote:
> > Provide an API for Bluetooth drivers to retrieve the Bluetooth Device
> > address (BD_ADDR) for a device. If the device node has a property
> > 'local-bd-address' the BD address is read from this property.
> > 
> > Signed-off-by: Matthias Kaehlcke <mka@...omium.org>
> > ---
> >  drivers/base/property.c  | 49 ++++++++++++++++++++++++++++++++++++++++
> >  include/linux/property.h |  4 ++++
> >  2 files changed, 53 insertions(+)
> > 
> > diff --git a/drivers/base/property.c b/drivers/base/property.c
> > index 240ab5230ff6..8fe546b9805a 100644
> > --- a/drivers/base/property.c
> > +++ b/drivers/base/property.c
> > @@ -18,6 +18,8 @@
> >  #include <linux/etherdevice.h>
> >  #include <linux/phy.h>
> >  
> > +#define BD_ADDR_LEN	6
> > +
> >  struct property_set {
> >  	struct device *dev;
> >  	struct fwnode_handle fwnode;
> > @@ -1315,6 +1317,53 @@ void *device_get_mac_address(struct device *dev, char *addr, int alen)
> >  }
> >  EXPORT_SYMBOL(device_get_mac_address);
> >  
> > +/**
> > + * fwnode_get_bd_address - Get the Bluetooth Device Address (BD_ADDR) from the
> > + *                         firmware node
> > + * @fwnode:	Pointer to the firmware node
> > + * @addr:	Address of buffer to store the BD address in
> > + * @alen:	Length of the buffer pointed to by addr, should be BD_ADDR_LEN
> > + *
> > + * Search the firmware node for 'local-bd-address'.
> > + *
> > + * All-zero BD addresses are rejected, because those could be properties
> > + * that exist in the firmware tables, but were not updated by the firmware. For
> > + * example, the DTS could define 'local-bd-address', with zero BD addresses.
> > + */
> > +int fwnode_get_bd_address(struct fwnode_handle *fwnode, u8 *addr, int alen)
> 
> How about using bdaddr_t instead? The original caller was casting it to u8
> probably just because there was no function specifically for this purpose.

I was considering that, but wasn't sure if it would be 'correct' to
include net/bluetooth/bluetooth.h (with the typdef of bdaddr_t) from
property.h since it is very frugal on headers and complex types.

That said I'd also prefer to use bdaddr_t if the API isn't limited to
basic data types on purpose.

> I wonder if this also should be made depend on CONFIG_BT. The fwnode
> framework is unconditionally a part of the kernel and it's not very big at
> the moment but adding stuff little by little will add up eventually.

Sounds good!

> > +{
> > +	u8 buf[BD_ADDR_LEN];
> > +	int ret;
> > +
> > +	if (alen != BD_ADDR_LEN)
> > +		return -EINVAL;
> > +
> > +	ret = fwnode_property_read_u8_array(fwnode, "local-bd-address",
> > +					    buf, alen);
> > +	if (ret < 0)
> > +		return ret;
> > +	if (is_zero_ether_addr(buf))
> > +		return -ENODATA;
> > +
> > +	memcpy(addr, buf, BD_ADDR_LEN);
> > +
> > +	return 0;
> > +}
> > +EXPORT_SYMBOL(fwnode_get_bd_address);
> > +
> > +/**
> > + * device_get_bd_address - Get the Bluetooth Device Address (BD_ADDR) for a
> > + *                         given device
> > + * @dev:	Pointer to the device
> > + * @addr:	Address of buffer to store the BD address in
> > + * @alen:	Length of the buffer pointed to by addr, should be BD_ADDR_LEN
> > + */
> > +int device_get_bd_address(struct device *dev, u8 *addr, int alen)
> > +{
> > +	return fwnode_get_bd_address(dev_fwnode(dev), addr, alen);
> > +}
> > +EXPORT_SYMBOL(device_get_bd_address);
> > +
> >  /**
> >   * fwnode_irq_get - Get IRQ directly from a fwnode
> >   * @fwnode:	Pointer to the firmware node
> > diff --git a/include/linux/property.h b/include/linux/property.h
> > index ac8a1ebc4c1b..4e2f1b276f4f 100644
> > --- a/include/linux/property.h
> > +++ b/include/linux/property.h
> > @@ -287,9 +287,13 @@ int device_get_phy_mode(struct device *dev);
> >  
> >  void *device_get_mac_address(struct device *dev, char *addr, int alen);
> >  
> > +int device_get_bd_address(struct device *dev, u8 *addr, int alen);
> > +
> >  int fwnode_get_phy_mode(struct fwnode_handle *fwnode);
> >  void *fwnode_get_mac_address(struct fwnode_handle *fwnode,
> >  			     char *addr, int alen);
> > +int fwnode_get_bd_address(struct fwnode_handle *fwnode,
> > +			  u8 *addr, int alen);
> 
> This would be a good opportunity to add a newline here, and avoid adding
> one after device_get_mac_address().

Will do

Thanks for the review!