Re: [PATCH 16/20] drm: add function to read vendor OUI

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Thu, Jul 13, 2017 at 10:34:26AM +0530, Sharma, Shashank wrote:
> Regads
> 
> Shashank
> 
> 
> On 7/12/2017 10:45 PM, Ville Syrjälä wrote:
> > On Mon, Jul 10, 2017 at 04:48:44PM +0530, Shashank Sharma wrote:
> >> This patch adds a helper function in DP dual mode layer to
> >> read the vendor's IEEE OUI signature from a Dual mode adapter.
> >> This will be used to differentiate between different LSPCON
> >> vendors, to address their custom programming requirements.
> > Can't we just read it from DPCD instead?
> You are right, as we have DPCD cached, we can do it from DPCD too, and 
> in fact that was my first implementation.
> But then I thought what if some driver doesn't cache DPCD, so thought it 
> would be good to have a helper function
> to check this out.
> If you think DPCD would be a better idea, I need not to touch DRM layer 
> at all, and this will be only I915 implementation.

Yeah, less code seems like a good thing. I think we might even have that
OUI stuff already read out and cached for other purposes.

> 
> - Shashank
> >
> >> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> >> Cc: Imre Deak <imre.deak@intel.com>
> >> Signed-off-by: Shashank Sharma <shashank.sharma@intel.com>
> >> ---
> >>   drivers/gpu/drm/drm_dp_dual_mode_helper.c | 24 ++++++++++++++++++++++++
> >>   include/drm/drm_dp_dual_mode_helper.h     |  4 +++-
> >>   2 files changed, 27 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/gpu/drm/drm_dp_dual_mode_helper.c b/drivers/gpu/drm/drm_dp_dual_mode_helper.c
> >> index 80e62f6..0b890dc 100644
> >> --- a/drivers/gpu/drm/drm_dp_dual_mode_helper.c
> >> +++ b/drivers/gpu/drm/drm_dp_dual_mode_helper.c
> >> @@ -396,6 +396,30 @@ const char *drm_dp_get_dual_mode_type_name(enum drm_dp_dual_mode_type type)
> >>   EXPORT_SYMBOL(drm_dp_get_dual_mode_type_name);
> >>   
> >>   /**
> >> + * drm_lspcon_get_vendor_oui: match vendor OUI signature
> >> + * @adapter: i2c adapter under action
> >> + * @vendor_id = 3 bytes of vendor OUI signature, LSB=lower byte
> >> + *
> >> + * Returns:
> >> + * Vendor OUI id if got one, 0 if not
> >> + */
> >> +uint32_t drm_lspcon_get_vendor_oui(struct i2c_adapter *adapter)
> >> +{
> >> +	uint8_t sign[3] = {0, };
> >> +	uint32_t oui = 0;
> >> +
> >> +	if (drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_LSPCON_OUI_OFFSET,
> >> +						sign, 3)) {
> >> +		DRM_ERROR("Can't identify vendor sign\n");
> >> +		return 0;
> >> +	}
> >> +
> >> +	oui = (sign[0] << 16) | (sign[1] << 8) | sign[2];
> >> +	return oui;
> >> +}
> >> +EXPORT_SYMBOL(drm_lspcon_get_vendor_oui);
> >> +
> >> +/**
> >>    * drm_lspcon_get_mode: Get LSPCON's current mode of operation by
> >>    * reading offset (0x80, 0x41)
> >>    * @adapter: I2C-over-aux adapter
> >> diff --git a/include/drm/drm_dp_dual_mode_helper.h b/include/drm/drm_dp_dual_mode_helper.h
> >> index 4c42db8..f81b526 100644
> >> --- a/include/drm/drm_dp_dual_mode_helper.h
> >> +++ b/include/drm/drm_dp_dual_mode_helper.h
> >> @@ -60,7 +60,8 @@
> >>   /* LSPCON specific registers, defined by MCA */
> >>   #define DP_DUAL_MODE_LSPCON_MODE_CHANGE		0x40
> >>   #define DP_DUAL_MODE_LSPCON_CURRENT_MODE		0x41
> >> -#define  DP_DUAL_MODE_LSPCON_MODE_PCON			0x1
> >> +#define DP_DUAL_MODE_LSPCON_MODE_PCON			0x1
> >> +#define DP_DUAL_MODE_LSPCON_OUI_OFFSET			0x11
> >>   
> >>   struct i2c_adapter;
> >>   
> >> @@ -116,4 +117,5 @@ int drm_lspcon_get_mode(struct i2c_adapter *adapter,
> >>   			enum drm_lspcon_mode *current_mode);
> >>   int drm_lspcon_set_mode(struct i2c_adapter *adapter,
> >>   			enum drm_lspcon_mode reqd_mode);
> >> +uint32_t drm_lspcon_get_vendor_oui(struct i2c_adapter *adapter);
> >>   #endif
> >> -- 
> >> 2.7.4

-- 
Ville Syrjälä
Intel OTC
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