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authorAkira Shimahara2020-05-11 22:37:08 +0200
committerGreg Kroah-Hartman2020-05-15 16:28:59 +0200
commit308bdb94de0c1abe7eac5193f58638b8aeaddf4b (patch)
tree27d4bc995e5d5b85c9e71d04d8b2365cef13820d /drivers/ide
parentb7bb6ca17a90f47c2fe2848531b5bbaf27a65ba7 (diff)
w1_therm: adding resolution sysfs entry
Adding resolution sysfs entry (RW) to get or set the device resolution Write values are managed as follow: * '9..12': resolution to set in bit * Anything else: do nothing Read values are : * '9..12': device resolution in bit * '-xx': xx is kernel error when reading the resolution Only supported devices will show the sysfs entry. A new family has been created for DS18S20 devices as they do not implement resolution feature. The resolution of each device is check when the device is discover by the bus master, in 'w1_therm_add_slave(struct w1_slave *)'. The status is stored in the device structure w1_therm_family_data so that the driver always knows the resolution of each device, which could be used later to determine the required conversion duration (resolution dependent). The resolution is re evaluate each time a user read or write the sysfs entry. To avoid looping through the w1_therm_families at run time, the pointer 'specific_functions' is set up to the correct 'w1_therm_family_converter' when the slave is added (which mean when it is discovered by the master). This initialization is done by a helper function 'device_family(struct w1_slave *sl)', and a dedicated macro 'SLAVE_SPECIFIC_FUNC(sl)' allow the access to the specific function of the slave device. 'read_scratchpad' and 'write_scratchpad' are the hardware functions to access the device RAM, as per protocol specification. It cancel the former 'precision' functions, which was only set and never read (so not stored in the device struct). Updating Documentation/ABI/testing/sysfs-driver-w1_therm accordingly. Signed-off-by: Akira Shimahara <akira215corp@gmail.com> Link: https://lore.kernel.org/r/20200511203708.410649-1-akira215corp@gmail.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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