libata: implement and use ops inheritance

libata lets low level drivers build ata_port_operations table and
register it with libata core layer.  This allows low level drivers
high level of flexibility but also burdens them with lots of
boilerplate entries.

This becomes worse for drivers which support related similar
controllers which differ slightly.  They share most of the operations
except for a few.  However, the driver still needs to list all
operations for each variant.  This results in large number of
duplicate entries, which is not only inefficient but also error-prone
as it becomes very difficult to tell what the actual differences are.

This duplicate boilerplates all over the low level drivers also make
updating the core layer exteremely difficult and error-prone.  When
compounded with multi-branched development model, it ends up
accumulating inconsistencies over time.  Some of those inconsistencies
cause immediate problems and fixed.  Others just remain there dormant
making maintenance increasingly difficult.

To rectify the problem, this patch implements ata_port_operations
inheritance.  To allow LLDs to easily re-use their own ops tables
overriding only specific methods, this patch implements poor man's
class inheritance.  An ops table has ->inherits field which can be set
to any ops table as long as it doesn't create a loop.  When the host
is started, the inheritance chain is followed and any operation which
isn't specified is taken from the nearest ancestor which has it
specified.  This operation is called finalization and done only once
per an ops table and the LLD doesn't have to do anything special about
it other than making the ops table non-const such that libata can
update it.

libata provides four base ops tables lower drivers can inherit from -
base, sata, pmp, sff and bmdma.  To avoid overriding these ops
accidentaly, these ops are declared const and LLDs should always
inherit these instead of using them directly.

After finalization, all the ops table are identical before and after
the patch except for setting .irq_handler to ata_interrupt in drivers
which didn't use to.  The .irq_handler doesn't have any actual effect
and the field will soon be removed by later patch.

* sata_sx4 is still using old style EH and currently doesn't take
  advantage of ops inheritance.

Signed-off-by: Tejun Heo <htejun@gmail.com>

1 files changed, 17 insertions, 243 deletions

diff --git a/drivers/ata/pata_legacy.c b/drivers/ata/pata_legacy.c
index 5329b954c5f2..2474068596f4 100644
--- a/drivers/ata/pata_legacy.c
+++ b/drivers/ata/pata_legacy.c
@@ -211,6 +211,11 @@ static struct scsi_host_template legacy_sht = {
         ATA_PIO_SHT(DRV_NAME),
 };
 
+static const struct ata_port_operations legacy_base_port_ops = {
+        .inherits       = &ata_sff_port_ops,
+        .cable_detect   = ata_cable_40wire,
+};
+
 /*
  *      These ops are used if the user indicates the hardware
  *      snoops the commands to decide on the mode and handles the
@@ -220,55 +225,14 @@ static struct scsi_host_template legacy_sht = {
  */
 
 static struct ata_port_operations simple_port_ops = {
-        .tf_load        = ata_tf_load,
-        .tf_read        = ata_tf_read,
-        .check_status   = ata_check_status,
-        .exec_command   = ata_exec_command,
-        .dev_select     = ata_std_dev_select,
-
-        .freeze         = ata_bmdma_freeze,
-        .thaw           = ata_bmdma_thaw,
-        .error_handler  = ata_bmdma_error_handler,
-        .post_internal_cmd = ata_bmdma_post_internal_cmd,
-        .cable_detect   = ata_cable_40wire,
-
-        .qc_prep        = ata_qc_prep,
-        .qc_issue       = ata_qc_issue_prot,
-
+        .inherits       = &legacy_base_port_ops,
         .data_xfer      = ata_data_xfer_noirq,
-
-        .irq_handler    = ata_interrupt,
-        .irq_clear      = ata_noop_irq_clear,
-        .irq_on         = ata_irq_on,
-
-        .port_start     = ata_sff_port_start,
 };
 
 static struct ata_port_operations legacy_port_ops = {
-        .set_mode       = legacy_set_mode,
-
-        .tf_load        = ata_tf_load,
-        .tf_read        = ata_tf_read,
-        .check_status   = ata_check_status,
-        .exec_command   = ata_exec_command,
-        .dev_select     = ata_std_dev_select,
-        .cable_detect   = ata_cable_40wire,
-
-        .freeze         = ata_bmdma_freeze,
-        .thaw           = ata_bmdma_thaw,
-        .error_handler  = ata_bmdma_error_handler,
-        .post_internal_cmd = ata_bmdma_post_internal_cmd,
-
-        .qc_prep        = ata_qc_prep,
-        .qc_issue       = ata_qc_issue_prot,
-
+        .inherits       = &legacy_base_port_ops,
         .data_xfer      = ata_data_xfer_noirq,
-
-        .irq_handler    = ata_interrupt,
-        .irq_clear      = ata_noop_irq_clear,
-        .irq_on         = ata_irq_on,
-
-        .port_start     = ata_sff_port_start,
+        .set_mode       = legacy_set_mode,
 };
 
 /*
@@ -359,30 +323,9 @@ static unsigned int pdc_data_xfer_vlb(struct ata_device *dev,
 }
 
 static struct ata_port_operations pdc20230_port_ops = {
+        .inherits       = &legacy_base_port_ops,
         .set_piomode    = pdc20230_set_piomode,
-
-        .tf_load        = ata_tf_load,
-        .tf_read        = ata_tf_read,
-        .check_status   = ata_check_status,
-        .exec_command   = ata_exec_command,
-        .dev_select     = ata_std_dev_select,
-
-        .freeze         = ata_bmdma_freeze,
-        .thaw           = ata_bmdma_thaw,
-        .error_handler  = ata_bmdma_error_handler,
-        .post_internal_cmd = ata_bmdma_post_internal_cmd,
-        .cable_detect   = ata_cable_40wire,
-
-        .qc_prep        = ata_qc_prep,
-        .qc_issue       = ata_qc_issue_prot,
-
         .data_xfer      = pdc_data_xfer_vlb,
-
-        .irq_handler    = ata_interrupt,
-        .irq_clear      = ata_noop_irq_clear,
-        .irq_on         = ata_irq_on,
-
-        .port_start     = ata_sff_port_start,
 };
 
 /*
@@ -413,30 +356,8 @@ static void ht6560a_set_piomode(struct ata_port *ap, struct ata_device *adev)
 }
 
 static struct ata_port_operations ht6560a_port_ops = {
+        .inherits       = &legacy_base_port_ops,
         .set_piomode    = ht6560a_set_piomode,
-
-        .tf_load        = ata_tf_load,
-        .tf_read        = ata_tf_read,
-        .check_status   = ata_check_status,
-        .exec_command   = ata_exec_command,
-        .dev_select     = ata_std_dev_select,
-
-        .freeze         = ata_bmdma_freeze,
-        .thaw           = ata_bmdma_thaw,
-        .error_handler  = ata_bmdma_error_handler,
-        .post_internal_cmd = ata_bmdma_post_internal_cmd,
-        .cable_detect   = ata_cable_40wire,
-
-        .qc_prep        = ata_qc_prep,
-        .qc_issue       = ata_qc_issue_prot,
-
-        .data_xfer      = ata_data_xfer,        /* Check vlb/noirq */
-
-        .irq_handler    = ata_interrupt,
-        .irq_clear      = ata_noop_irq_clear,
-        .irq_on         = ata_irq_on,
-
-        .port_start     = ata_sff_port_start,
 };
 
 /*
@@ -478,30 +399,8 @@ static void ht6560b_set_piomode(struct ata_port *ap, struct ata_device *adev)
 }
 
 static struct ata_port_operations ht6560b_port_ops = {
+        .inherits       = &legacy_base_port_ops,
         .set_piomode    = ht6560b_set_piomode,
-
-        .tf_load        = ata_tf_load,
-        .tf_read        = ata_tf_read,
-        .check_status   = ata_check_status,
-        .exec_command   = ata_exec_command,
-        .dev_select     = ata_std_dev_select,
-
-        .freeze         = ata_bmdma_freeze,
-        .thaw           = ata_bmdma_thaw,
-        .error_handler  = ata_bmdma_error_handler,
-        .post_internal_cmd = ata_bmdma_post_internal_cmd,
-        .cable_detect   = ata_cable_40wire,
-
-        .qc_prep        = ata_qc_prep,
-        .qc_issue       = ata_qc_issue_prot,
-
-        .data_xfer      = ata_data_xfer,    /* FIXME: Check 32bit and noirq */
-
-        .irq_handler    = ata_interrupt,
-        .irq_clear      = ata_noop_irq_clear,
-        .irq_on         = ata_irq_on,
-
-        .port_start     = ata_sff_port_start,
 };
 
 /*
@@ -599,30 +498,8 @@ static void opti82c611a_set_piomode(struct ata_port *ap,
 
 
 static struct ata_port_operations opti82c611a_port_ops = {
+        .inherits       = &legacy_base_port_ops,
         .set_piomode    = opti82c611a_set_piomode,
-
-        .tf_load        = ata_tf_load,
-        .tf_read        = ata_tf_read,
-        .check_status   = ata_check_status,
-        .exec_command   = ata_exec_command,
-        .dev_select     = ata_std_dev_select,
-
-        .freeze         = ata_bmdma_freeze,
-        .thaw           = ata_bmdma_thaw,
-        .error_handler  = ata_bmdma_error_handler,
-        .post_internal_cmd = ata_bmdma_post_internal_cmd,
-        .cable_detect   = ata_cable_40wire,
-
-        .qc_prep        = ata_qc_prep,
-        .qc_issue       = ata_qc_issue_prot,
-
-        .data_xfer      = ata_data_xfer,
-
-        .irq_handler    = ata_interrupt,
-        .irq_clear      = ata_noop_irq_clear,
-        .irq_on         = ata_irq_on,
-
-        .port_start     = ata_sff_port_start,
 };
 
 /*
@@ -731,30 +608,9 @@ static unsigned int opti82c46x_qc_issue_prot(struct ata_queued_cmd *qc)
 }
 
 static struct ata_port_operations opti82c46x_port_ops = {
+        .inherits       = &legacy_base_port_ops,
         .set_piomode    = opti82c46x_set_piomode,
-
-        .tf_load        = ata_tf_load,
-        .tf_read        = ata_tf_read,
-        .check_status   = ata_check_status,
-        .exec_command   = ata_exec_command,
-        .dev_select     = ata_std_dev_select,
-
-        .freeze         = ata_bmdma_freeze,
-        .thaw           = ata_bmdma_thaw,
-        .error_handler  = ata_bmdma_error_handler,
-        .post_internal_cmd = ata_bmdma_post_internal_cmd,
-        .cable_detect   = ata_cable_40wire,
-
-        .qc_prep        = ata_qc_prep,
         .qc_issue       = opti82c46x_qc_issue_prot,
-
-        .data_xfer      = ata_data_xfer,
-
-        .irq_handler    = ata_interrupt,
-        .irq_clear      = ata_noop_irq_clear,
-        .irq_on         = ata_irq_on,
-
-        .port_start     = ata_sff_port_start,
 };
 
 static void qdi6500_set_piomode(struct ata_port *ap, struct ata_device *adev)
@@ -916,84 +772,22 @@ static int qdi_port(struct platform_device *dev,
 }
 
 static struct ata_port_operations qdi6500_port_ops = {
+        .inherits       = &legacy_base_port_ops,
         .set_piomode    = qdi6500_set_piomode,
-
-        .tf_load        = ata_tf_load,
-        .tf_read        = ata_tf_read,
-        .check_status   = ata_check_status,
-        .exec_command   = ata_exec_command,
-        .dev_select     = ata_std_dev_select,
-
-        .freeze         = ata_bmdma_freeze,
-        .thaw           = ata_bmdma_thaw,
-        .error_handler  = ata_bmdma_error_handler,
-        .post_internal_cmd = ata_bmdma_post_internal_cmd,
-        .cable_detect   = ata_cable_40wire,
-
-        .qc_prep        = ata_qc_prep,
         .qc_issue       = qdi_qc_issue_prot,
-
         .data_xfer      = vlb32_data_xfer,
-
-        .irq_handler    = ata_interrupt,
-        .irq_clear      = ata_noop_irq_clear,
-        .irq_on         = ata_irq_on,
-
-        .port_start     = ata_sff_port_start,
 };
 
 static struct ata_port_operations qdi6580_port_ops = {
+        .inherits       = &legacy_base_port_ops,
         .set_piomode    = qdi6580_set_piomode,
-
-        .tf_load        = ata_tf_load,
-        .tf_read        = ata_tf_read,
-        .check_status   = ata_check_status,
-        .exec_command   = ata_exec_command,
-        .dev_select     = ata_std_dev_select,
-
-        .freeze         = ata_bmdma_freeze,
-        .thaw           = ata_bmdma_thaw,
-        .error_handler  = ata_bmdma_error_handler,
-        .post_internal_cmd = ata_bmdma_post_internal_cmd,
-        .cable_detect   = ata_cable_40wire,
-
-        .qc_prep        = ata_qc_prep,
-        .qc_issue       = ata_qc_issue_prot,
-
         .data_xfer      = vlb32_data_xfer,
-
-        .irq_handler    = ata_interrupt,
-        .irq_clear      = ata_noop_irq_clear,
-        .irq_on         = ata_irq_on,
-
-        .port_start     = ata_sff_port_start,
 };
 
 static struct ata_port_operations qdi6580dp_port_ops = {
+        .inherits       = &legacy_base_port_ops,
         .set_piomode    = qdi6580dp_set_piomode,
-
-        .tf_load        = ata_tf_load,
-        .tf_read        = ata_tf_read,
-        .check_status   = ata_check_status,
-        .exec_command   = ata_exec_command,
-        .dev_select     = ata_std_dev_select,
-
-        .freeze         = ata_bmdma_freeze,
-        .thaw           = ata_bmdma_thaw,
-        .error_handler  = ata_bmdma_error_handler,
-        .post_internal_cmd = ata_bmdma_post_internal_cmd,
-        .cable_detect   = ata_cable_40wire,
-
-        .qc_prep        = ata_qc_prep,
-        .qc_issue       = qdi_qc_issue_prot,
-
         .data_xfer      = vlb32_data_xfer,
-
-        .irq_handler    = ata_interrupt,
-        .irq_clear      = ata_noop_irq_clear,
-        .irq_on         = ata_irq_on,
-
-        .port_start     = ata_sff_port_start,
 };
 
 static DEFINE_SPINLOCK(winbond_lock);
@@ -1062,29 +856,9 @@ static int winbond_port(struct platform_device *dev,
 }
 
 static struct ata_port_operations winbond_port_ops = {
+        .inherits       = &legacy_base_port_ops,
         .set_piomode    = winbond_set_piomode,
-
-        .tf_load        = ata_tf_load,
-        .tf_read        = ata_tf_read,
-        .check_status   = ata_check_status,
-        .exec_command   = ata_exec_command,
-        .dev_select     = ata_std_dev_select,
-
-        .freeze         = ata_bmdma_freeze,
-        .thaw           = ata_bmdma_thaw,
-        .error_handler  = ata_bmdma_error_handler,
-        .post_internal_cmd = ata_bmdma_post_internal_cmd,
-        .cable_detect   = ata_cable_40wire,
-
-        .qc_prep        = ata_qc_prep,
-        .qc_issue       = ata_qc_issue_prot,
-
         .data_xfer      = vlb32_data_xfer,
-
-        .irq_clear      = ata_noop_irq_clear,
-        .irq_on         = ata_irq_on,
-
-        .port_start     = ata_sff_port_start,
 };
 
 static struct legacy_controller controllers[] = {