Re: [dpdk-dev] [PATCH v2 1/6] lib/eal: implement the family of rte bit operation APIs

[Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>]

Hi Joyce,
	Thanks for the patch, few comments.

<snip>

> 
> There are a lot functions of bit operations scattered and duplicated in PMDs,
> consolidating them into a common API family is necessary. Furthermore, the
> bit operation is mostly applied to the IO devices, so use __ATOMIC_ACQ_REL
> to ensure the ordering.
The APIs are not taking memory ordering as a parameter. This presents the same problem as the rte_atomic_xxx APIs. IMO, the APIs should take memory ordering as a parameter.

> 
> Signed-off-by: Joyce Kong <joyce.kong@arm.com>
> Reviewed-by: Gavin Hu <gavin.hu@arm.com>
> ---
>  lib/librte_eal/common/Makefile                |   1 +
>  lib/librte_eal/common/include/rte_io_bitops.h | 112
> ++++++++++++++++++++++++++
>  lib/librte_eal/common/meson.build             |   1 +
>  3 files changed, 114 insertions(+)
>  create mode 100644 lib/librte_eal/common/include/rte_io_bitops.h
> 
> diff --git a/lib/librte_eal/common/Makefile
> b/lib/librte_eal/common/Makefile index a00d4fc..3831313 100644
> --- a/lib/librte_eal/common/Makefile
> +++ b/lib/librte_eal/common/Makefile
> @@ -18,6 +18,7 @@ INC += rte_malloc.h rte_keepalive.h rte_time.h  INC +=
> rte_service.h rte_service_component.h  INC += rte_bitmap.h rte_vfio.h
> rte_hypervisor.h rte_test.h  INC += rte_reciprocal.h rte_fbarray.h rte_uuid.h
> +INC += rte_io_bitops.h
> 
>  GENERIC_INC := rte_atomic.h rte_byteorder.h rte_cycles.h rte_prefetch.h
> GENERIC_INC += rte_memcpy.h rte_cpuflags.h diff --git
> a/lib/librte_eal/common/include/rte_io_bitops.h
> b/lib/librte_eal/common/include/rte_io_bitops.h
> new file mode 100644
> index 0000000..5f778b8
> --- /dev/null
> +++ b/lib/librte_eal/common/include/rte_io_bitops.h
> @@ -0,0 +1,112 @@
> +/* SPDX-License-Identifier: BSD-3-Clause
> + * Copyright(c) 2019 Arm Limited
> + */
> +
> +#ifndef _RTE_IO_BITOPS_H_
> +#define _RTE_IO_BITOPS_H_
> +
> +/**
> + * @file
> + * Bit Operations
> + *
> + * This file defines a generic API for bit operations.
> + */
> +
> +#include <rte_lcore.h>
> +
> +/**
> + * Get a bit.
> + *
> + * @param nr
> + *   The bit to get.
> + * @param addr
> + *   The address to count from.
> + * @return
> + *   The value of the bit.
> + */
> +static inline int32_t
> +rte_io_get_bit(uint32_t nr, uint64_t *addr) {
> +	return __atomic_load_n(addr, __ATOMIC_ACQUIRE) & (1UL << nr); }
Some use cases might need 'relaxed' memory order for this API. So, the user of this API should be able to provide the memory order.

> +
> +/**
> + * Set a bit to 1.
> + *
> + * @param nr
> + *   The bit to set.
> + * @param addr
> + *   The address to count from.
> + */
> +static inline void
> +rte_io_set_bit(uint32_t nr, uint64_t *addr) {
> +	__atomic_fetch_or(addr, (1UL << nr), __ATOMIC_ACQ_REL); }
Some use cases might need 'release' or 'relaxed' memory order.
Similar requirements apply to other APIs too.

> +
> +/**
> + * Set a bit to 0.
> + *
> + * @param nr
> + *   The bit to set.
> + * @param addr
> + *   The address to count from.
> + */
> +static inline void
> +rte_io_clear_bit(int32_t nr, uint64_t *addr) {
> +	__atomic_fetch_and(addr, ~(1UL << nr), __ATOMIC_ACQ_REL); }
> +
> +/**
> + * Test if a bit is 1.
> + *
> + * @param nr
> + *   The bit to test.
> + * @param addr
> + *   The address to count from.
> + * @return
> + *   1 if the bit is 1; else 0.
> + */
> +static inline int32_t
> +rte_io_test_bit(int32_t nr, uint64_t *addr) {
> +	return (__atomic_load_n(addr, __ATOMIC_ACQUIRE) & (1UL <<
> nr)) != 0; }
> +
> +/**
> + * Set a bit to 1 and return its old value.
> + *
> + * @param nr
> + *   The bit to set.
> + * @param addr
> + *   The address to count from.
> + * @return
> + *   The old value of the bit.
> + */
> +static inline int32_t
> +rte_io_test_and_set_bit(int32_t nr, uint64_t *addr) {
> +	unsigned long mask = (1UL << nr);
> +
> +	return __atomic_fetch_or(addr, mask, __ATOMIC_ACQ_REL) &
> mask; }
> +
> +/**
> + * Set a bit to 0 and return its old value.
> + *
> + * @param nr
> + *   The bit to set.
> + * @param addr
> + *   The address to count from.
> + * @return
> + *   The old value of the bit.
> + */
> +static inline int32_t
> +rte_io_test_and_clear_bit(int32_t nr, uint64_t *addr) {
> +	unsigned long mask = (1UL << nr);
> +
> +	return __atomic_fetch_and(addr, ~mask, __ATOMIC_ACQ_REL) &
> mask; }
> +#endif /* _RTE_IO_BITOPS_H_ */
> diff --git a/lib/librte_eal/common/meson.build
> b/lib/librte_eal/common/meson.build
> index 386577c..0a65d04 100644
> --- a/lib/librte_eal/common/meson.build
> +++ b/lib/librte_eal/common/meson.build
> @@ -52,6 +52,7 @@ common_headers = files(
>  	'include/rte_alarm.h',
>  	'include/rte_branch_prediction.h',
>  	'include/rte_bus.h',
> +	'include/rte_io_bitops.h',
>  	'include/rte_bitmap.h',
>  	'include/rte_class.h',
>  	'include/rte_common.h',
> --
> 2.7.4