summaryrefslogtreecommitdiffstats
path: root/Documentation/driver-api/eisa.rst
diff options
context:
space:
mode:
authorLinus Torvalds <torvalds@linux-foundation.org>2026-08-24 08:46:03 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2026-08-24 08:46:03 -0700
commitcf9610f9116d55c5a66ef9f1faecacabd93a9322 (patch)
tree757a3d280760c654767631cab5ad8af2d86d1848 /Documentation/driver-api/eisa.rst
downloadlinux-stable-cf9610f9116d55c5a66ef9f1faecacabd93a9322.tar.gz
linux-stable-cf9610f9116d55c5a66ef9f1faecacabd93a9322.zip
Merge tag 'pinctrl-v7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-pinctrlgrafted
Pull pin control updates from Linus Walleij: "Core changes: - Use the non-blocking mux_state_try_select() in the generic MUX pin control back-end - Free pin maps on pinctrl_generic_to_map() failure in the core helpers New hardware pin control: - Qualcomm Maili TLMM SoC, PMG1110 PMIC, and Eliza LPASS LPI TLMM SoC (this is for the low power audio, LPASS = Low Power Audio SubSystem portions) - Upboard support on top of the Intel pin controller - Apple T6030 and T6031 support (just compatible strings) - Samsung Exynos 8855 SoC - Mediatek MT6858 SoC - Rockchip RK3308B and RV1106 SoCs - Airoha EN7523 and AN7563 SoCs Improvements: - Qualcomm TLMM GPIOs are unconditionally marked as wakeup capable - Qualcomm improvements on top of the Qualcomm PDC (power domain controller) irqchip improvements from tglx:s tree - Qualcomm IPQ806x and IPQ9650 non-urgent pin grop fixups - The NPCM8xx driver has been put into shape fixing many pin and group definitions - Some non-urgent Tegra 264 pin assignments are fixed up - Some non-urgent fixups to Airoha AN7581 and AN7583 registers and pin assignments, missing features etc" * tag 'pinctrl-v7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-pinctrl: (130 commits) dt-bindings: pinctrl: Convert TI DA850 pupd to DT schema pinctrl: meson: sync some modify from A4 pinctrl: meson: a4: Add input enable pin configuration pinctrl: realtek: rtd1625: remove unused group name spdif_sel pinctrl: realtek: rtd1625: fix base_bit for VE4 GPIO 13 dt-bindings: pinctrl: microchip,pic32mzda-pinctrl: Convert to DT schema Revert "Merge branch 'ib-rsk7204' into devel" pinctrl: rockchip: Add RV1106 pinctrl support dt-bindings: pinctrl: rockchip: Add RV1106 compatible pinctrl: rockchip: Decode drive strength in the get function pinctrl: fix PINCTRL_GENERIC_MUX not always being selectable pinctrl: airoha: add support of an7563 SoC dt-bindings: pinctrl: airoha: add support of an7563 pin controller pinctrl: airoha: try to find chip scu node by phandle first pinctrl: airoha: add support of en7523 SoC dt-bindings: pinctrl: airoha: add support of en7523 pin controller pinctrl: airoha: an7583: add support for olt pinmux pinctrl: airoha: an7583: add support for pon_alt pinmux pinctrl: airoha: an7583: add support for npu_uart pinmux dt-bindings: pinctrl: airoha: an7583: add missed features ...
Diffstat (limited to 'Documentation/driver-api/eisa.rst')
-rw-r--r--Documentation/driver-api/eisa.rst232
1 files changed, 232 insertions, 0 deletions
diff --git a/Documentation/driver-api/eisa.rst b/Documentation/driver-api/eisa.rst
new file mode 100644
index 000000000..e98b21b60
--- /dev/null
+++ b/Documentation/driver-api/eisa.rst
@@ -0,0 +1,232 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+================
+EISA bus support
+================
+
+:Author: Marc Zyngier <maz@wild-wind.fr.eu.org>
+
+This document groups random notes about porting EISA drivers to the
+new EISA/sysfs API.
+
+Starting from version 2.5.59, the EISA bus is almost given the same
+status as other much more mainstream buses such as PCI or USB. This
+has been possible through sysfs, which defines a nice enough set of
+abstractions to manage buses, devices and drivers.
+
+Although the new API is quite simple to use, converting existing
+drivers to the new infrastructure is not an easy task (mostly because
+detection code is generally also used to probe ISA cards). Moreover,
+most EISA drivers are among the oldest Linux drivers so, as you can
+imagine, some dust has settled here over the years.
+
+The EISA infrastructure is made up of three parts:
+
+ - The bus code implements most of the generic code. It is shared
+ among all the architectures that the EISA code runs on. It
+ implements bus probing (detecting EISA cards available on the bus),
+ allocates I/O resources, allows fancy naming through sysfs, and
+ offers interfaces for driver to register.
+
+ - The bus root driver implements the glue between the bus hardware
+ and the generic bus code. It is responsible for discovering the
+ device implementing the bus, and setting it up to be latter probed
+ by the bus code. This can go from something as simple as reserving
+ an I/O region on x86, to the rather more complex, like the hppa
+ EISA code. This is the part to implement in order to have EISA
+ running on an "new" platform.
+
+ - The driver offers the bus a list of devices that it manages, and
+ implements the necessary callbacks to probe and release devices
+ whenever told to.
+
+Every function/structure below lives in <linux/eisa.h>, which depends
+heavily on <linux/device.h>.
+
+Bus root driver
+===============
+
+::
+
+ int eisa_root_register (struct eisa_root_device *root);
+
+The eisa_root_register function is used to declare a device as the
+root of an EISA bus. The eisa_root_device structure holds a reference
+to this device, as well as some parameters for probing purposes::
+
+ struct eisa_root_device {
+ struct device *dev; /* Pointer to bridge device */
+ struct resource *res;
+ unsigned long bus_base_addr;
+ int slots; /* Max slot number */
+ int force_probe; /* Probe even when no slot 0 */
+ u64 dma_mask; /* from bridge device */
+ int bus_nr; /* Set by eisa_root_register */
+ struct resource eisa_root_res; /* ditto */
+ };
+
+============= ======================================================
+node used for eisa_root_register internal purpose
+dev pointer to the root device
+res root device I/O resource
+bus_base_addr slot 0 address on this bus
+slots max slot number to probe
+force_probe Probe even when slot 0 is empty (no EISA mainboard)
+dma_mask Default DMA mask. Usually the bridge device dma_mask.
+bus_nr unique bus id, set by eisa_root_register
+============= ======================================================
+
+Driver
+======
+
+::
+
+ int eisa_driver_register (struct eisa_driver *edrv);
+ void eisa_driver_unregister (struct eisa_driver *edrv);
+
+Clear enough ?
+
+::
+
+ struct eisa_device_id {
+ char sig[EISA_SIG_LEN];
+ unsigned long driver_data;
+ };
+
+ struct eisa_driver {
+ const struct eisa_device_id *id_table;
+ struct device_driver driver;
+ };
+
+=============== ====================================================
+id_table an array of NULL terminated EISA id strings,
+ followed by an empty string. Each string can
+ optionally be paired with a driver-dependent value
+ (driver_data).
+
+driver a generic driver, such as described in
+ Documentation/driver-api/driver-model/driver.rst. Only .name,
+ .probe and .remove members are mandatory.
+=============== ====================================================
+
+An example is the 3c59x driver::
+
+ static struct eisa_device_id vortex_eisa_ids[] = {
+ { "TCM5920", EISA_3C592_OFFSET },
+ { "TCM5970", EISA_3C597_OFFSET },
+ { "" }
+ };
+
+ static struct eisa_driver vortex_eisa_driver = {
+ .id_table = vortex_eisa_ids,
+ .driver = {
+ .name = "3c59x",
+ .probe = vortex_eisa_probe,
+ .remove = vortex_eisa_remove
+ }
+ };
+
+Device
+======
+
+The sysfs framework calls .probe and .remove functions upon device
+discovery and removal (note that the .remove function is only called
+when driver is built as a module).
+
+Both functions are passed a pointer to a 'struct device', which is
+encapsulated in a 'struct eisa_device' described as follows::
+
+ struct eisa_device {
+ struct eisa_device_id id;
+ int slot;
+ int state;
+ unsigned long base_addr;
+ struct resource res[EISA_MAX_RESOURCES];
+ u64 dma_mask;
+ struct device dev; /* generic device */
+ };
+
+======== ============================================================
+id EISA id, as read from device. id.driver_data is set from the
+ matching driver EISA id.
+slot slot number which the device was detected on
+state set of flags indicating the state of the device. Current
+ flags are EISA_CONFIG_ENABLED and EISA_CONFIG_FORCED.
+res set of four 256 bytes I/O regions allocated to this device
+dma_mask DMA mask set from the parent device.
+dev generic device (see Documentation/driver-api/driver-model/device.rst)
+======== ============================================================
+
+You can get the 'struct eisa_device' from 'struct device' using the
+'to_eisa_device' macro.
+
+Misc stuff
+==========
+
+::
+
+ void eisa_set_drvdata (struct eisa_device *edev, void *data);
+
+Stores data into the device's driver_data area.
+
+::
+
+ void *eisa_get_drvdata (struct eisa_device *edev):
+
+Gets the pointer previously stored into the device's driver_data area.
+
+::
+
+ int eisa_get_region_index (void *addr);
+
+Returns the region number (0 <= x < EISA_MAX_RESOURCES) of a given
+address.
+
+Kernel parameters
+=================
+
+eisa_bus.enable_dev
+ A comma-separated list of slots to be enabled, even if the firmware
+ set the card as disabled. The driver must be able to properly
+ initialize the device in such conditions.
+
+eisa_bus.disable_dev
+ A comma-separated list of slots to be disabled, even if the firmware
+ set the card as enabled. The driver won't be called to handle this
+ device.
+
+virtual_root.force_probe
+ Force the probing code to probe EISA slots even when it cannot find an
+ EISA compliant mainboard (nothing appears on slot 0). Defaults to 0
+ (don't force), and set to 1 (force probing) when
+ CONFIG_EISA_VLB_PRIMING is set.
+
+Random notes
+============
+
+Converting an EISA driver to the new API mostly involves *deleting*
+code (since probing is now in the core EISA code). Unfortunately, most
+drivers share their probing routine between ISA, and EISA. Special
+care must be taken when ripping out the EISA code, so other buses
+won't suffer from these surgical strikes...
+
+You *must not* expect any EISA device to be detected when returning
+from eisa_driver_register, since the chances are that the bus has not
+yet been probed. In fact, that's what happens most of the time (the
+bus root driver usually kicks in rather late in the boot process).
+Unfortunately, most drivers are doing the probing by themselves, and
+expect to have explored the whole machine when they exit their probe
+routine.
+
+For example, switching your favorite EISA SCSI card to the "hotplug"
+model is "the right thing"(tm).
+
+Thanks
+======
+
+I'd like to thank the following people for their help:
+
+- Xavier Benigni for lending me a wonderful Alpha Jensen,
+- James Bottomley, Jeff Garzik for getting this stuff into the kernel,
+- Andries Brouwer for contributing numerous EISA ids,
+- Catrin Jones for coping with far too many machines at home.