Registering radeon display connectors fails due to missing adapter name. The problem surfaced after this commit to Linus' kernel tree:

commit 2236baa75f704851d3cd3310569058151acb1f06 Author: Jean Delvare khali@linux-fr.org Date: Mon Nov 15 22:40:38 2010 +0100

i2c: Sanity checks on adapter registration

Make sure I2C adapters being registered have the required struct fields set. If they don't, problems will happen later.

Signed-off-by: Jean Delvare khali@linux-fr.org

diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c index d231f68..6b4cc56 100644 --- a/drivers/i2c/i2c-core.c +++ b/drivers/i2c/i2c-core.c @@ -848,6 +848,18 @@ static int i2c_register_adapter(struct i2c_adapter *adap) goto out_list; }

+ /* Sanity checks */ + if (unlikely(adap->name[0] == '\0')) { + pr_err("i2c-core: Attempt to register an adapter with " + "no name!\n"); + return -EINVAL; + } + if (unlikely(!adap->algo)) { + pr_err("i2c-core: Attempt to register adapter '%s' with " + "no algo!\n", adap->name); + return -EINVAL; + } + rt_mutex_init(&adap->bus_lock); mutex_init(&adap->userspace_clients_lock); INIT_LIST_HEAD(&adap->userspace_clients);

dmesg output that shows the problem: [    3.870533] i2c-core: Attempt to register an adapter with no name! [    3.870591] [drm] Failed to register i2c DP-auxch [    3.870647] i2c-core: Attempt to register an adapter with no name! [    3.870708] [drm] Failed to register i2c DP-auxch [    3.870821] [drm] Radeon Display Connectors [    3.870824] [drm] Connector 0: [    3.870825] [drm]   DVI-I [    3.870827] [drm]   HPD1 [    3.870829] [drm]   DDC: 0x7e20 0x7e20 0x7e24 0x7e24 0x7e28 0x7e28 0x7e2c 0x7e2c [    3.870831] [drm]   Encoders: [    3.870833] [drm]     CRT2: INTERNAL_KLDSCP_DAC2 [    3.870834] [drm]     DFP1: INTERNAL_UNIPHY

The corresponding output was originally like this: [    3.781507] [drm] Radeon Display Connectors [    3.781510] [drm] Connector 0: [    3.781511] [drm]   DisplayPort [    3.781513] [drm]   HPD2 [    3.781515] [drm]   DDC: 0x7e50 0x7e50 0x7e54 0x7e54 0x7e58 0x7e58 0x7e5c 0x7e5c [    3.781517] [drm]   Encoders: [    3.781518] [drm]     DFP2: INTERNAL_UNIPHY1 [    3.781520] [drm] Connector 1: [    3.781521] [drm]   DisplayPort [    3.781522] [drm]   HPD3 [    3.781524] [drm]   DDC: 0x7f10 0x7f10 0x7f14 0x7f14 0x7f18 0x7f18 0x7f1c 0x7f1c [    3.781526] [drm]   Encoders: [    3.781528] [drm]     DFP3: INTERNAL_UNIPHY1 [    3.781529] [drm] Connector 2: [    3.781531] [drm]   DVI-I [    3.781532] [drm]   HPD1 [    3.781534] [drm]   DDC: 0x7e20 0x7e20 0x7e24 0x7e24 0x7e28 0x7e28 0x7e2c 0x7e2c [    3.781535] [drm]   Encoders: [    3.781537] [drm]     CRT2: INTERNAL_KLDSCP_DAC2 [    3.781538] [drm]     DFP1: INTERNAL_UNIPHY

A change like this fixes the problem:

diff --git a/drivers/gpu/drm/radeon/radeon_i2c.c b/drivers/gpu/drm/radeon/radeon_i2c.c index 0cfbba0..65d05c0 100644 --- a/drivers/gpu/drm/radeon/radeon_i2c.c +++ b/drivers/gpu/drm/radeon/radeon_i2c.c @@ -946,6 +946,7 @@ struct radeon_i2c_chan *radeon_i2c_create_dp(struct drm_device *dev,         i2c->rec = *rec;         i2c->adapter.owner = THIS_MODULE;         i2c->dev = dev; +       sprintf(i2c->adapter.name, "Radeon i2c bus %s", name);         i2c_set_adapdata(&i2c->adapter, i2c);         i2c->adapter.algo_data = &i2c->algo.dp;         i2c->algo.dp.aux_ch = radeon_dp_i2c_aux_ch;