dmaengine: idxd: move dsa_drv support to compatible mode

Hello Dave Jiang,

The patch 6e7f3ee97bbe: "dmaengine: idxd: move dsa_drv support to compatible mode" from Jul 15, 2021, leads to the following static checker warning:

drivers/dma/idxd/compat.c:66 bind_store()
error: uninitialized symbol 'alt_drv'.

drivers/dma/idxd/compat.c

    33  static ssize_t bind_store(struct device_driver *drv, const char *buf, size_t count)
    34  {
    35          struct bus_type *bus = drv->bus;
    36          struct device *dev;
    37          struct device_driver *alt_drv;
    38          int rc = -ENODEV;
    39          struct idxd_dev *idxd_dev;
    40  
    41          dev = bus_find_device_by_name(bus, NULL, buf);
    42          if (!dev || dev->driver || drv != &dsa_drv.drv)
    43                  return -ENODEV;
    44  
    45          idxd_dev = confdev_to_idxd_dev(dev);
    46          if (is_idxd_dev(idxd_dev)) {
    47                  alt_drv = driver_find("idxd", bus);
    48                  if (!alt_drv)
    49                          return -ENODEV;
    50          } else if (is_idxd_wq_dev(idxd_dev)) {
                           ^^^^^^^^^^^^^^^^^^^^^^^^

Presumably this condition is always true but the static checker is not smart enough to figure it out.

    51                  struct idxd_wq *wq = confdev_to_wq(dev);
    52  
    53                  if (is_idxd_wq_kernel(wq)) {
    54                          alt_drv = driver_find("dmaengine", bus);
    55                          if (!alt_drv)
    56                                  return -ENODEV;
    57                  } else if (is_idxd_wq_user(wq)) {
    58                          alt_drv = driver_find("user", bus);
    59                          if (!alt_drv)
    60                                  return -ENODEV;
    61                  } else {
    62                          return -ENODEV;
    63                  }
    64          }
    65  
    66          rc = device_driver_attach(alt_drv, dev);
    67          if (rc < 0)
    68                  return rc;
    69  
    70          return count;
    71  }

regards,
dan carpenter

Thanks Dan! This patch should make static checker happy:

https://lore.kernel.org/dmaengine/162689250332.2114335.636367120454420852.stgit@djiang5-desk3.ch.intel.com/T/#u